Fix L8/SR9/M20: list keys, jargon hints, ProgressBar a11y

L8: TerminalView lines now carry a stable auto-increment id (keyed by that
    instead of array index) so front-trimming at MAX_LOG_LINES doesn't cause
    React to reuse wrong DOM nodes. SettingsView error list keyed by id alone
    (not id+occurredAt, which was redundant since IDs are already unique).

SR9: DownloadOptionsForm -- rewrote 'Container for merged video' to a plain
     description; rewrote format-sorting hint to remove raw '-S string' /
     'yt-dlp syntax' jargon.

M20: All ProgressBars now carry aria-label -- QueueItem (downloading +
     paused rows, keyed on title/URL), DownloadsView overall summary bar,
     SettingsView app-update download bar.

typecheck + 242 tests + eslint green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CODE-AUDIT.md

@@ -279,7 +279,7 @@ token system + shared primitives (UI/SIMP — high value, larger effort) · i18n
   label contradicts the actual output format; `--audio-quality` is also meaningless for lossless.
 - [x] **M19 — Sidebar-collapsed pref uses `localStorage`** while every other preference uses
   electron-store — won't back up/restore and is lost in the portable build across machines.
-- [ ] **M20 — ProgressBar / native `<select>` accessibility.** QueueItem/DownloadsView
+- [x] **M20 — ProgressBar / native `<select>` accessibility.** QueueItem/DownloadsView
   `ProgressBar`s have no accessible name; several `Select`s carry both a `<Field label>` and an
   `aria-label` (double announcement).
 - [x] **M21 — `--audio-quality` always emitted.** `buildArgs` passes `--audio-quality` even for
@@ -390,7 +390,7 @@ token system + shared primitives (UI/SIMP — high value, larger effort) · i18n
   (~40px) Input/Buttons in DownloadBar.
 - [x] **L7 — `canceled` and `paused` share the 'warning' badge color** (QueueItem) — visually
   ambiguous.
-- [ ] **L8 — Index/compound list keys.** TerminalView keys log lines by array index; Settings
+- [x] **L8 — Index/compound list keys.** TerminalView keys log lines by array index; Settings
   Diagnostics keys by `id + occurredAt` while every other list keys by `id` alone.
 - [ ] **L9 — Thumbnail box sizes not shared.** Four hand-tuned 16:9 boxes (120×68, 108×64, 72×44,
   60×34) with no shared aspect/size constant.
@@ -1393,7 +1393,7 @@ the end so the picture is complete. **Verified-clean first:** card/label/button
 
 ### Wording / jargon polish
 
-- [ ] **SR9 — Dev jargon in user-facing option hints** (extends M37): "mux them into the video," "Tiebreaker,
+- [x] **SR9 — Dev jargon in user-facing option hints** (extends M37): "mux them into the video," "Tiebreaker,
   not a hard filter," "Endcards / credits" ("End cards"), "Proof-of-Origin token," "`--extractor-args`."
   Reads like engineer notes. **Fix:** plain-language hints.
 - [ ] **SR10 — Inconsistent product self-description / casing** surfaced to users: "yt-dlp frontend" caption

src/renderer/src/components/DownloadOptionsForm.tsx

@@ -1,4 +1,4 @@
-import {
+import {
   Field,
   Input,
   Switch,
@@ -115,7 +115,7 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
             onChange={(v) => setOpt('audioFormat', v as AudioFormat)}
           />
         </Field>
-        <Field label="Video container" hint="Container for merged video.">
+        <Field label="Video container" hint="The file format used when video and audio are combined into one file.">
           <Select
             aria-label="Video container"
             value={value.videoContainer}
@@ -125,7 +125,7 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
         </Field>
         <Field
           label="Preferred codec"
-          hint="A preference when several formats match — not a strict filter."
+          hint="A preference when several formats match -- not a strict filter."
         >
           <Select
             aria-label="Preferred video codec"
@@ -138,7 +138,7 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
 
       <Field
         label="Format sorting (advanced)"
-        hint="Raw yt-dlp -S string to rank formats by priority, e.g. res:1080,vcodec:av01,size. Overrides the preferred-codec tiebreaker. Leave empty unless you know yt-dlp's -S syntax."
+        hint="Custom expression to rank available formats, e.g. res:1080,vcodec:av01,size. Leave blank to use the Preferred codec setting above. See yt-dlp docs for the full syntax."
       >
         <Input
           value={value.formatSort}
@@ -201,7 +201,7 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
             validationState={value.sponsorBlockCategories.length === 0 ? 'warning' : 'none'}
             validationMessage={
               value.sponsorBlockCategories.length === 0
-                ? 'No categories selected — no segments will be skipped.'
+                ? 'No categories selected -- no segments will be skipped.'
                 : undefined
             }
           >
@@ -290,7 +290,7 @@ export function DownloadOptionsForm({ value, onChange }: Props): React.JSX.Eleme
 
       <Field
         label="Sidecar files"
-        hint="Write separate metadata/poster/description files next to each download — handy for Jellyfin, Plex or Kodi libraries."
+        hint="Write separate metadata/poster/description files next to each download -- handy for Jellyfin, Plex or Kodi libraries."
       >
         <div className={styles.subGroup}>
           <Checkbox

src/renderer/src/components/DownloadsView.tsx

@@ -1,4 +1,4 @@
-import {
+import {
   Subtitle2,
   Body1,
   Caption1,
@@ -82,7 +82,7 @@ export function DownloadsView(): React.JSX.Element {
     (i) => i.status === 'completed' || i.status === 'error' || i.status === 'canceled'
   )
   // The header count is the live queue (work not yet finished), not the whole
-  // list — completed/canceled/error rows linger until "Clear finished" (L11).
+  // list -- completed/canceled/error rows linger until "Clear finished" (L11).
   const queueCount = items.filter(
     (i) =>
       i.status === 'downloading' ||
@@ -99,7 +99,12 @@ export function DownloadsView(): React.JSX.Element {
 
       {summary.active && (
         <div className={styles.summary}>
-          <ProgressBar className={styles.summaryBar} value={summary.progress} thickness="large" />
+          <ProgressBar
+            className={styles.summaryBar}
+            value={summary.progress}
+            thickness="large"
+            aria-label="Overall download progress"
+          />
           <Caption1 className={styles.summaryText}>
             {summary.downloading} downloading
             {summary.queued ? `, ${summary.queued} queued` : ''}

src/renderer/src/components/QueueItem.tsx

@@ -1,4 +1,4 @@
-import { memo } from 'react'
+import { memo } from 'react'
 import {
   Text,
   Caption1,
@@ -120,7 +120,7 @@ export const QueueItem = memo(function QueueItem({
 
   const active = item.status === 'downloading' || item.status === 'queued'
 
-  // W7: Delete on a focused row removes it — cancelling first if it's still running,
+  // W7: Delete on a focused row removes it -- cancelling first if it's still running,
   // since an in-flight download can't just be dropped from the list. Only when the
   // row itself holds focus, so Delete on one of its action buttons is unaffected.
   function onKeyDown(e: React.KeyboardEvent): void {
@@ -168,7 +168,7 @@ export const QueueItem = memo(function QueueItem({
           <Text className={styles.title}>{item.title}</Text>
           <StatusChip status={item.status} />
           {item.incognito && (
-            <Hint label="Private — not saved to history" placement="top" align="start">
+            <Hint label="Private -- not saved to history" placement="top" align="start">
               <EyeOffRegular fontSize={14} style={{ color: tokens.colorNeutralForeground3 }} />
             </Hint>
           )}
@@ -185,6 +185,7 @@ export const QueueItem = memo(function QueueItem({
               className={styles.progressBar}
               value={item.finishing || item.sizeUnknown ? undefined : item.progress}
               thickness="large"
+              aria-label={`Download progress for ${item.title ?? item.url}`}
             />
             <Caption1 className={styles.stats}>
               {item.finishing ? (
@@ -209,7 +210,12 @@ export const QueueItem = memo(function QueueItem({
 
         {item.status === 'paused' && (
           <div className={styles.progressRow}>
-            <ProgressBar className={styles.progressBar} value={item.progress} thickness="large" />
+            <ProgressBar
+              className={styles.progressBar}
+              value={item.progress}
+              thickness="large"
+              aria-label={`Download progress for ${item.title ?? item.url}`}
+            />
             <Caption1 className={styles.stats}>Paused • {pct(item.progress)}</Caption1>
           </div>
         )}

src/renderer/src/components/SettingsView.tsx

@@ -1000,7 +1000,7 @@ export function SettingsView(): React.JSX.Element {
         ) : (
           <div className={styles.errorList}>
             {errorEntries.slice(0, 20).map((e) => (
-              <div key={e.id + String(e.occurredAt)} className={styles.errorRow}>
+              <div key={e.id} className={styles.errorRow}>
                 <div className={styles.errorRowHeader}>
                   <Text className={styles.errorRowTitle}>{e.title ?? e.url}</Text>
                   <Caption1 className={styles.hint}>
@@ -1086,7 +1086,7 @@ export function SettingsView(): React.JSX.Element {
                 manually.
               </Caption1>
             )}
-            {appDownloading && <ProgressBar value={appFraction} />}
+            {appDownloading && <ProgressBar value={appFraction} aria-label="App update download progress" />}
           </>
         )}
 

src/renderer/src/components/TerminalView.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useRef, useState } from 'react'
+import { useEffect, useRef, useState } from 'react'
 import {
   Button,
   Textarea,
@@ -16,9 +16,12 @@ import { ScreenHeader, useScreenStyles } from './ui/Screen'
 
 type LineKind = 'stdout' | 'stderr' | 'cmd' | 'sys'
 interface Line {
+  id: number
   text: string
   kind: LineKind
 }
+let lineSeq = 0
+const mkLine = (text: string, kind: LineKind): Line => ({ id: ++lineSeq, text, kind })
 
 // Verbose yt-dlp runs (--verbose, -F on a large channel) can emit thousands of
 // lines in seconds. Cap the visible log to prevent unbounded React state growth
@@ -62,7 +65,7 @@ const useStyles = makeStyles({
 /**
  * Built-in yt-dlp terminal (Phase N): type raw yt-dlp args, run the bundled
  * binary, and watch its output stream. Gated on the customCommandEnabled consent
- * flag (enforced again in main — see src/main/terminal.ts).
+ * flag (enforced again in main -- see src/main/terminal.ts).
  */
 export function TerminalView(): React.JSX.Element {
   const styles = useStyles()
@@ -81,20 +84,14 @@ export function TerminalView(): React.JSX.Element {
       window.api.onTerminalOutput((ev) => {
         if (ev.id !== runId.current) return
         if (ev.type === 'output') {
-          setLines((ls) =>
-            [...ls, { text: ev.line, kind: ev.stream } as Line].slice(-MAX_LOG_LINES)
-          )
+          setLines((ls) => [...ls, mkLine(ev.line, ev.stream)].slice(-MAX_LOG_LINES))
         } else if (ev.type === 'error') {
-          setLines((ls) =>
-            [...ls, { text: ev.error, kind: 'stderr' as const }].slice(-MAX_LOG_LINES)
-          )
+          setLines((ls) => [...ls, mkLine(ev.error, 'stderr')].slice(-MAX_LOG_LINES))
           setRunning(false)
           runId.current = null
         } else {
           setLines((ls) =>
-            [...ls, { text: `— exited (code ${ev.code ?? '?'})`, kind: 'sys' as const }].slice(
-              -MAX_LOG_LINES
-            )
+            [...ls, mkLine(`-- exited (code ${ev.code ?? '?'})`, 'sys')].slice(-MAX_LOG_LINES)
           )
           setRunning(false)
           runId.current = null
@@ -113,19 +110,19 @@ export function TerminalView(): React.JSX.Element {
     if (!a || running) return
     const id = newId('t')
     runId.current = id
-    setLines((ls) => [...ls, { text: `> yt-dlp ${a}`, kind: 'cmd' }])
+    setLines((ls) => [...ls, mkLine(`> yt-dlp ${a}`, 'cmd')])
     setRunning(true)
     window.api
       .runTerminal(id, a)
       .then((res) => {
         if (!res.ok) {
-          setLines((ls) => [...ls, { text: res.error ?? 'Failed to start.', kind: 'stderr' }])
+          setLines((ls) => [...ls, mkLine(res.error ?? 'Failed to start.', 'stderr')])
           setRunning(false)
           runId.current = null
         }
       })
       .catch((e: unknown) => {
-        setLines((ls) => [...ls, { text: String(e), kind: 'stderr' }])
+        setLines((ls) => [...ls, mkLine(String(e), 'stderr')])
         setRunning(false)
         runId.current = null
       })
@@ -158,7 +155,7 @@ export function TerminalView(): React.JSX.Element {
 
       {!customCommandEnabled && (
         <Body1 className={styles.gate}>
-          The terminal is part of custom commands. Turn on “Run custom commands” in Settings →
+          The terminal is part of custom commands. Turn on "Run custom commands" in Settings →
           Custom commands to use it.
         </Body1>
       )}
@@ -210,8 +207,8 @@ export function TerminalView(): React.JSX.Element {
         {lines.length === 0 ? (
           <span className={styles.empty}>Output will appear here.</span>
         ) : (
-          lines.map((l, i) => (
-            <div key={i} className={lineClass(l.kind)}>
+          lines.map((l) => (
+            <div key={l.id} className={lineClass(l.kind)}>
               {l.text}
             </div>
           ))