docs: sync to Claude Code v2.1.110 (TUI, push notifications, session recap) (#80)

* docs: sync to Claude Code v2.1.110 with TUI, push notifications, session recap, and new commands

- 01-slash-commands: add /tui, /focus, /recap, /undo, /proactive to command table and recent changes
- 07-plugins: document monitors manifest key for background monitor support (v2.1.105)
- 09-advanced-features: add TUI mode, push notifications, session recap, ENABLE_PROMPT_CACHING_1H
- 10-cli: add --exclude-dynamic-system-prompt-sections flag and CLAUDE_CODE_PERFORCE_MODE env var
- CATALOG.md: update command counts (55+→60+, 63+→68+), add 5 new command rows
- All 12 files: bump footer to April 16, 2026 / Claude Code Version 2.1.110

* fix(catalog): correct version tags for /proactive, /recap, /undo commands

/proactive was added in v2.1.105, /recap and /undo in v2.1.108 — not v2.1.110.
Only /tui and /focus were introduced in v2.1.110.

08-checkpoints/README.md

@@ -315,8 +315,8 @@ Key benefits:
 Remember: checkpoints are not a replacement for git. Use checkpoints for rapid experimentation and git for permanent code changes.
 
 ---
-**Last Updated**: April 11, 2026
-**Claude Code Version**: 2.1.101
+**Last Updated**: April 16, 2026
+**Claude Code Version**: 2.1.110
 **Sources**:
 - https://code.claude.com/docs/en/checkpointing
 **Compatible Models**: Claude Sonnet 4.6, Claude Opus 4.6, Claude Haiku 4.5