feat: optimize skills + add pipeline handoff chaining across 9 skills

asr-transcribe-to-text:
- Add local MLX transcription path (macOS Apple Silicon, 15-27x realtime)
- Add bundled script transcribe_local_mlx.py with max_tokens=200000
- Add local_mlx_guide.md with benchmarks and truncation trap docs
- Auto-detect platform and recommend local vs remote mode
- Fix audio extraction format (MP3 → WAV 16kHz mono PCM)
- Add Step 5: recommend transcript-fixer after transcription

transcript-fixer:
- Optimize SKILL.md from 289 → 153 lines (best practices compliance)
- Move FALSE_POSITIVE_RISKS (40 lines) to references/false_positive_guide.md
- Move Example Session to references/example_session.md
- Improve description for better triggering (226 → 580 chars)
- Add handoff to meeting-minutes-taker

skill-creator:
- Add "Pipeline Handoff" pattern to Skill Writing Guide
- Add pipeline check reminder in Step 4 (Edit the Skill)

Pipeline handoffs added to 8 skills forming 6 chains:
- youtube-downloader → asr-transcribe-to-text → transcript-fixer → meeting-minutes-taker → pdf/ppt-creator
- deep-research → fact-checker → pdf/ppt-creator
- doc-to-markdown → docs-cleaner / fact-checker
- claude-code-history-files-finder → continue-claude-work

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

doc-to-markdown/SKILL.md

@@ -171,3 +171,16 @@ brew install pandoc
 - `references/heavy-mode-guide.md` - Detailed Heavy Mode documentation
 - `references/tool-comparison.md` - Tool capabilities comparison
 - `references/conversion-examples.md` - Batch operation examples
+
+## Next Step: Clean Up Converted Content
+
+After converting documents to markdown, suggest cleanup:
+
+```
+Conversion complete: [N] files converted to markdown.
+
+Options:
+A) Clean up docs — run /docs-cleaner to consolidate redundant content (Recommended if multiple files)
+B) Check facts — run /fact-checker to verify claims in the converted content
+C) No thanks — the markdown conversion is sufficient
+```