Implement /gcal Google Calendar integration

Components:
- commands/gcal.md: Slash command with aliases (calendar, cal)
- skills/gcal/SKILL.md: Usage patterns, routing logic, output formats
- mcp/delegation/gcal_delegate.py: Python API wrapper with tiered delegation

Features:
- Subcommands: today, tomorrow, week, next, summary
- Smart default (today before 6pm, tomorrow after)
- Hybrid interface (subcommands + natural language)
- Haiku tier for fetch/format, Sonnet tier for analysis

Requires OAuth setup: enable Calendar API and authorize.

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

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

skills/gcal/SKILL.md

@@ -0,0 +1,131 @@
+---
+name: gcal
+description: Google Calendar read access — agenda overview, event details, smart summaries
+allowed-tools:
+  - Bash
+---
+
+# Google Calendar Skill
+
+Access Google Calendar via Python API. Uses OAuth credentials at `~/.gmail-mcp/`.
+
+## Command Routing
+
+### 1. Exact Subcommand Match (priority)
+
+| Input | Action |
+|-------|--------|
+| `today` | Today's agenda |
+| `tomorrow` | Tomorrow's agenda |
+| `week` | Next 7 days, grouped by day |
+| `next` | Next upcoming event only |
+| `summary` | Sonnet-powered week analysis |
+
+### 2. Natural Language Fallback
+
+| Input | Routes To |
+|-------|-----------|
+| "what's on today", "today's meetings" | today |
+| "this week", "next 7 days" | week |
+| "next meeting", "what's next" | next |
+| "am I busy tomorrow", "tomorrow's schedule" | tomorrow |
+| "overview", "summarize my week" | summary |
+
+### 3. Smart Default (no args)
+
+- Before 6pm → today
+- After 6pm → tomorrow
+
+### 4. Ambiguous Input
+
+Ask for clarification rather than guess.
+
+## Delegated Operations
+
+Use the delegation helper for cost-efficient operations:
+
+```bash
+GCAL_PY=~/.claude/mcp/gmail/venv/bin/python
+HELPER=~/.claude/mcp/delegation/gcal_delegate.py
+
+# Haiku tier - fetch and format
+$GCAL_PY $HELPER today
+$GCAL_PY $HELPER tomorrow
+$GCAL_PY $HELPER week
+$GCAL_PY $HELPER next
+
+# Sonnet tier - analyze (spawns claude --model sonnet)
+$GCAL_PY $HELPER summary
+```
+
+## Delegation Tiers
+
+| Subcommand | Tier | Reason |
+|------------|------|--------|
+| today, tomorrow, week, next | Haiku | Fetch + format only |
+| summary | Sonnet | Requires understanding/analysis |
+
+## Output Format
+
+The helper returns JSON. Format for user as:
+
+### Simple List (today/tomorrow/next)
+
+```
+📅 Today — Thursday, Jan 2
+
+  9:00 AM   Team standup (30m)
+            📍 Zoom · 👥 5 attendees
+
+ 10:30 AM   1:1 with Sarah (45m)
+            📍 Conference Room B
+
+No more events today.
+```
+
+### Grouped by Day (week)
+
+```
+📅 This Week — Jan 2-8
+
+━━━ Thursday, Jan 2 ━━━
+  9:00 AM   Team standup (30m)
+  2:00 PM   Project review (1h)
+
+━━━ Friday, Jan 3 ━━━
+  11:00 AM  Client call (1h)
+```
+
+### Context Fields (show when available)
+
+- 📍 Location or meeting link
+- 👥 Attendee count
+- 📝 Description snippet (first ~50 chars)
+
+## Error Handling
+
+### Missing Calendar Scope
+
+If helper reports scope error:
+
+```
+Calendar access not authorized. To fix:
+1. Delete cached token: rm ~/.gmail-mcp/token.json
+2. Run /gcal today to re-authenticate with Calendar scope
+```
+
+### No Events
+
+```
+📅 Today — Thursday, Jan 2
+
+No events scheduled.
+```
+
+## Policy
+
+- Read-only operations only
+- Show context (attendees, location) by default
+- Summarize results, don't dump raw data
+- Start with lowest capable model tier
+- Escalate only when task complexity requires