Add documentation, PreCompact hook, gcal improvements, and marketplace

Documentation:
- Add commands/README.md documenting all slash commands
- Add skills/README.md documenting skill structure and patterns
- Add .claude-plugin/marketplace.json for local dev testing

Hooks:
- Add PreCompact hook to remind about context preservation
- Update hooks/README.md with new hook

GCal improvements:
- Add scripts/next_event.py for single event lookup
- Update SKILL.md with simplified format and allowed-tools: Read

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

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

skills/README.md

@@ -0,0 +1,105 @@
+# Skills
+
+Agent skills that extend Claude's capabilities. Model-invoked (Claude decides when to use them).
+
+## Available Skills
+
+| Skill | Description | Scripts |
+|-------|-------------|---------|
+| `gmail` | Gmail read access | `check_unread.py`, `check_urgent.py`, `search.py` |
+| `gcal` | Google Calendar access | `agenda.py`, `next_event.py` |
+| `k8s-quick-status` | Kubernetes cluster health | `quick-status.sh` |
+| `sysadmin-health` | Arch Linux health check | `health-check.sh` |
+| `usage` | Session usage tracking | `usage_report.py` |
+| `programmer-add-project` | Register projects | (workflow only) |
+
+## Skill Structure
+
+Each skill uses the "Resources Pattern":
+
+```
+skills/skill-name/
+├── SKILL.md            # Main instructions (required)
+├── scripts/            # Executable helpers
+│   ├── action1.py
+│   └── action2.sh
+└── references/         # Documentation
+    └── patterns.md
+```
+
+## Skill Format
+
+```yaml
+---
+name: skill-name
+description: What it does. Use when [trigger conditions].
+allowed-tools:
+  - Bash
+  - Read
+---
+
+# Skill Name
+
+## Quick Commands
+
+```bash
+./scripts/main-action.py [args]
+```
+
+## Request Routing
+
+| User Request | Action |
+|--------------|--------|
+| "do X" | Run script with args |
+
+## Policy
+
+- Read-only / Write allowed
+- Model tier preferences
+```
+
+## Key Elements
+
+### Description
+
+Critical for discovery. Include:
+- What the skill does
+- When Claude should use it (trigger phrases)
+
+### allowed-tools
+
+Restricts which tools Claude can use:
+- `Bash` - Run commands/scripts
+- `Read` - Read files
+- `Write` - Write files
+- `Edit` - Edit files
+
+### Scripts
+
+Standalone executables that do the work:
+- Python: `#!/usr/bin/env python3`
+- Bash: `#!/bin/bash`
+- Must be executable: `chmod +x`
+
+### References
+
+Supporting documentation:
+- Query patterns
+- API reference
+- Examples
+
+## Adding a Skill
+
+1. Create `skills/name/SKILL.md`
+2. Add scripts to `skills/name/scripts/`
+3. Make scripts executable
+4. Update `component-registry.json` with triggers
+5. Test: ask Claude something that should trigger it
+
+## Skill vs Command
+
+| Aspect | Skill | Command |
+|--------|-------|---------|
+| **Invocation** | Claude decides | User types `/command` |
+| **Discovery** | Based on description | Explicit |
+| **Use case** | Domain expertise | Quick actions |