[codex] Fix playback pause and scroll behavior

[Talljack]

What changed

• Keep Listen controls in the visible viewport with an independently scrollable transcript.
• Preserve word and sentence highlights while paused; resume the existing browser or audio playback instead of restarting.
• Align browser speech boundaries with their real character offsets and add regression coverage.
• Make Write references and typing areas independently scrollable, and keep Speak conversations pinned to the latest message.

Root cause

Listen Pause called the destructive TTS stop path, which canceled the utterance and cleared the playback state. Highlight rendering was also conditioned on active playback.

Validation

• pnpm test src/components/read-aloud/read-aloud-content.test.tsx src/lib/read-aloud-playback.test.ts
• PLAYWRIGHT_BASE_URL=http://127.0.0.1:3119 PLAYWRIGHT_REUSE_EXISTING_SERVER=true pnpm exec playwright test e2e/listen.spec.ts --workers=1 --reporter=line
• pnpm typecheck
• pnpm lint
• pnpm build

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Project	Deployment	Actions	Updated (UTC)
echo-type	Ready	Preview, Comment	Jul 29, 2026 1:26pm