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/uk.settings.ts

@@ -1504,6 +1504,9 @@ export const settingsDict = {
   "settings.voice.page.preview.browserVoiceFallback": "голос вашого браузера",
   "settings.voice.page.preview.voiceLine": "Привіт! Я {voiceName}. Ось як я звучу.",
   "settings.voice.page.preview.customServerLine": "Привіт! Це попередній перегляд спеціального сервера TTS.",
+  "settings.voice.page.field.ttsInputMode": "Режим вводу TTS",
+  "settings.voice.page.field.ttsInputModeSanitized": "Очищений текст",
+  "settings.voice.page.field.ttsInputModeRaw": "Сирий Markdown",
   "settings.openchamber.visual.section.colorMode": "Режим теми",
   "settings.openchamber.visual.section.mobileLayout": "Мобільний макет",
   "settings.openchamber.visual.option.mobileLayout.default": "Попередній",