feat: add voice transcription as nanorepo skill (#326)

Add voice transcription skill package at
.claude/skills/add-voice-transcription/ so it can be applied via the
skills engine. Skill adds src/transcription.ts (OpenAI Whisper), modifies
whatsapp.ts to detect/transcribe voice notes, and includes intent files,
3 test cases, and 8 skill validation tests.

Also fixes skills engine runNpmInstall() to use --legacy-peer-deps,
needed for any skill adding deps with Zod v3 peer requirements.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/add-voice-transcription/modify/src/channels/whatsapp.test.ts.intent.md

@@ -0,0 +1,26 @@
+# Intent: src/channels/whatsapp.test.ts modifications
+
+## What changed
+Added mock for the transcription module and 3 new test cases for voice message handling.
+
+## Key sections
+
+### Mocks (top of file)
+- Added: `vi.mock('../transcription.js', ...)` with `isVoiceMessage` and `transcribeAudioMessage` mocks
+- Added: `import { transcribeAudioMessage } from '../transcription.js'` for test assertions
+
+### Test cases (inside "message handling" describe block)
+- Changed: "handles message with no extractable text (e.g. voice note without caption)" → "transcribes voice messages"
+  - Now expects `[Voice: Hello this is a voice message]` instead of empty content
+- Added: "falls back when transcription returns null" — expects `[Voice Message - transcription unavailable]`
+- Added: "falls back when transcription throws" — expects `[Voice Message - transcription failed]`
+
+## Invariants (must-keep)
+- All existing test cases for text, extendedTextMessage, imageMessage, videoMessage unchanged
+- All connection lifecycle tests unchanged
+- All LID translation tests unchanged
+- All outgoing queue tests unchanged
+- All group metadata sync tests unchanged
+- All ownsJid and setTyping tests unchanged
+- All existing mocks (config, logger, db, fs, child_process, baileys) unchanged
+- Test helpers (createTestOpts, triggerConnection, triggerDisconnect, triggerMessages, connectChannel) unchanged