docs: Update README, CLAUDE, and AGENTS for NotebookLM skills

- Update skill count from 30 to 34
- Add NotebookLM Tools section (50-59) with 4 skills
- Add NotebookLM agent routing guide in AGENTS.md
- Update directory layout to include 50-53

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

AGENTS.md

@@ -139,6 +139,33 @@ Task 2: general-purpose - "Implement the planned skill"  # Needs Task 1 result
 - Skills export data to Working with AI database
 - Check schema compatibility before creating pages
 
+### NotebookLM Skills (50-59)
+
+- Use `notebooklm` CLI for all operations (installed via `pip install notebooklm-py`)
+- Requires authentication: `notebooklm login` (browser-based Google OAuth)
+- Four specialized skills for different workflows:
+
+| Skill | Purpose | Key Commands |
+|-------|---------|--------------|
+| 50-notebooklm-agent | Q&A with citations | `notebooklm ask "question" --json` |
+| 51-notebooklm-automation | Notebook management | `notebooklm create`, `source add`, `list` |
+| 52-notebooklm-studio | Content generation | `notebooklm generate audio/video/quiz` |
+| 53-notebooklm-research | Research workflows | `notebooklm source add-research "topic"` |
+
+**Long-running operations:** Use subagent pattern for generation/research:
+```
+# Start generation (non-blocking)
+notebooklm generate audio "instructions" --json
+
+# Spawn subagent to wait and download
+Task(
+  prompt="Wait for artifact {id} then download: notebooklm artifact wait {id} && notebooklm download audio ./output.mp3",
+  subagent_type="general-purpose"
+)
+```
+
+**Parallel workflows:** Set `NOTEBOOKLM_HOME` per agent to avoid context conflicts.
+
 ### Reference Curator Skills (90-99)
 
 - Use **reference-curator-pipeline** for full automated curation workflows