feat: CJK word count, pipeline timing, history modal, auto-mute, auto-dictionary

[WEIFENG2333]

Summary

• Universal word count: New countWords() utility supporting mixed CJK + Latin text (CJK characters count individually, Latin words by whitespace)
• Pipeline timing: STT and LLM call durations recorded and displayed in history detail view with colored badges
• History detail modal: Redesigned from full-page navigation to modal overlay popup with backdrop blur
• Auto-mute: System audio auto-muted during recording (macOS osascript, Linux pactl), with state restore
• Auto-dictionary learning: Proper nouns, brand names, and technical terms auto-extracted from transcriptions and added to personal dictionary
• OCR prompt redesign: Structured extraction (APP, TASK, KEY TERMS, TEXT CONTEXT) instead of freeform description
• Settings UI: New toggles for auto-mute (Audio) and auto-learn dictionary (Context)
• i18n: All new strings translated in both en/zh
• CLAUDE.md: Comprehensive rewrite with synchronization checklists, naming conventions, and common pitfalls

Changed files (20 files, +1463/-374)

• src/utils/wordCount.ts — New CJK-aware word counting utility
• electron/main.ts — Auto-mute, auto-dictionary extraction, pipeline timing
• electron/llm-service.ts — Redesigned OCR prompt
• electron/preload.ts — New onDictionaryAutoAdded event
• electron/config-store.ts — New config defaults
• src/types/config.ts — Added timing, auto-learn fields to types
• src/types/electron.d.ts — Updated PipelineResult + new event type
• src/services/pipeline.ts — Pass through timing + auto-learned terms
• src/hooks/useRecorder.ts — Use countWords, save timing to history
• src/pages/HistoryPage.tsx — Modal overlay + timing display + auto-learned terms
• src/pages/settings/AudioSettings.tsx — Auto-mute toggle
• src/pages/settings/ContextSettings.tsx — Auto-learn dictionary toggle
• src/i18n/locales/{en,zh}.json — New translation keys

Test plan

• Verify CJK word counting: "你好 world" should count as 4 (2 CJK + 1 Latin + "world")
• Verify pipeline timing shows in history detail modal (STT/LLM duration badges)
• Verify history detail opens as modal overlay, closes on backdrop click or X
• Verify auto-mute toggle in Audio settings persists
• Verify auto-learn toggle in Context settings persists
• Verify typecheck and build pass (confirmed locally)

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