feat(tts): add TTS buttons to PlanView and FilesView markdown preview with configurable input mode (#1443)

Add TTS controls to markdown preview surfaces so users can listen to plans
and markdown files directly from the preview toolbar.

Changes:
- Add read-aloud / stop buttons to PlanView markdown preview.
- Add read-aloud / stop buttons to FilesView markdown preview for markdown files.
- Respect the existing showMessageTTSButtons preference in both preview views.
- Add a persisted ttsInputMode setting with sanitized/raw modes.
- Keep sanitized mode as the default for backward compatibility.
- Allow raw markdown only for server TTS providers that can handle markdown.
- Always use sanitized text for browser and macOS say fallback paths.
- Add Voice Settings controls for TTS input mode.
- Add i18n keys for the new preview buttons and setting labels.
- Merge latest main and preserve newer FilesView toolbar/editor changes.

Validation:
- bun test packages/ui/src/stores/useConfigStore.test.ts packages/ui/src/components/chat/message/parts/ToolPart.test.ts packages/web/server/lib/tts/routes.test.js
- bun run type-check
- bun run lint
- git diff --check

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/lib/i18n/messages/pl.ts

@@ -714,6 +714,10 @@ export const dict: Record<I18nKey, string> = {
   'chat.messageBody.tts.stopSpeaking': 'Przestań mówić',
   'chat.messageBody.tts.readAloud': 'Czytaj na głos',
   'chat.messageBody.tts.readAloudWithProvider': 'Czytaj na głos ({provider} voice)',
+  'planView.tts.readAloud': 'Czytaj plan na głos',
+  'planView.tts.stopSpeaking': 'Zatrzymaj czytanie',
+  'filesView.tts.readAloud': 'Czytaj plik na głos',
+  'filesView.tts.stopSpeaking': 'Zatrzymaj czytanie',
   'chat.messageBody.toast.noProject': 'Nie znaleziono projektu dla tej sesji',
   'chat.messageBody.toast.savePlanFailed': 'Nie udało się zapisać planu',
   'chat.messageBody.toast.planSaved': 'Plan zapisany',