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/stores/useConfigStore.ts

@@ -683,6 +683,7 @@ interface ConfigStore {
     sttSilenceHoldMs: number;
     sttTranscribeOnStop: boolean;
     showMessageTTSButtons: boolean;
+    ttsInputMode: 'sanitized' | 'raw';
     voiceModeEnabled: boolean;
     // Summarization settings
     summarizeMessageTTS: boolean;
@@ -710,6 +711,7 @@ interface ConfigStore {
     setSttSilenceHoldMs: (ms: number) => void;
     setSttTranscribeOnStop: (enabled: boolean) => void;
     setShowMessageTTSButtons: (show: boolean) => void;
+    setTtsInputMode: (mode: 'sanitized' | 'raw') => void;
     setVoiceModeEnabled: (enabled: boolean) => void;
     setSummarizeMessageTTS: (enabled: boolean) => void;
     setSummarizeVoiceConversation: (enabled: boolean) => void;
@@ -978,6 +980,13 @@ export const useConfigStore = create<ConfigStore>()(
                     }
                     return false;
                 })(),
+                ttsInputMode: (() => {
+                    if (typeof window !== 'undefined') {
+                        const saved = localStorage.getItem('ttsInputMode');
+                        if (saved === 'raw') return 'raw' as const;
+                    }
+                    return 'sanitized' as const;
+                })(),
                 // Voice mode enabled - load from localStorage or default to false
                 voiceModeEnabled: (() => {
                     if (typeof window !== 'undefined') {
@@ -2286,6 +2295,13 @@ export const useConfigStore = create<ConfigStore>()(
                     }
                 },
 
+                setTtsInputMode: (mode: 'sanitized' | 'raw') => {
+                    set({ ttsInputMode: mode });
+                    if (typeof window !== 'undefined') {
+                        localStorage.setItem('ttsInputMode', mode);
+                    }
+                },
+
                 setVoiceModeEnabled: (enabled: boolean) => {
                     set({ voiceModeEnabled: enabled });
                     if (typeof window !== 'undefined') {