Add hooks and refactor skills to use resources pattern

Phase 1 of plugin-structure refactor:

- Add hooks/hooks.json for SessionStart automation
- Refactor gmail skill:
  - Extract inline scripts to scripts/check_unread.py, check_urgent.py, search.py
  - Add references/query-patterns.md for query documentation
  - Simplify SKILL.md to reference scripts instead of inline code
- Add gcal/scripts/agenda.py for direct calendar access
- Make all scripts executable

This follows the "Skill with Bundled Resources" pattern from
developing-claude-code-plugins best practices.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

skills/gmail/references/query-patterns.md

@@ -0,0 +1,57 @@
+# Gmail Query Patterns
+
+## Basic Queries
+
+| Request | Gmail Query |
+|---------|-------------|
+| Unread | `is:unread` |
+| Last N days | `newer_than:Nd` |
+| From sender | `from:email@example.com` |
+| To recipient | `to:email@example.com` |
+| With attachments | `has:attachment` |
+| Important | `is:important` |
+| Starred | `is:starred` |
+| In inbox | `in:inbox` |
+
+## Urgent/Priority
+
+| Pattern | Query |
+|---------|-------|
+| Urgent keywords | `subject:(urgent OR asap OR "action required")` |
+| Important + unread | `is:important is:unread` |
+| Time-sensitive | `subject:(deadline OR "due date" OR "end of day")` |
+
+## Sender Patterns
+
+| Pattern | Query |
+|---------|-------|
+| GitHub notifications | `from:github.com` |
+| Google alerts | `from:googlealerts-noreply@google.com` |
+| Calendar invites | `from:calendar-notification@google.com` |
+| Newsletters | `category:promotions` |
+
+## Combining Queries
+
+Queries can be combined:
+
+```
+is:unread newer_than:7d from:github.com
+is:unread (subject:urgent OR is:important) newer_than:3d
+has:attachment from:client@example.com newer_than:30d
+```
+
+## Date Queries
+
+| Pattern | Query |
+|---------|-------|
+| Last 24 hours | `newer_than:1d` |
+| Last week | `newer_than:7d` |
+| Last month | `newer_than:30d` |
+| Specific date | `after:2024/01/01 before:2024/01/31` |
+
+## Size Queries
+
+| Pattern | Query |
+|---------|-------|
+| Large attachments | `larger:10M` |
+| Small emails | `smaller:100K` |