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>

.claude-plugin/marketplace.json

@@ -0,0 +1,18 @@
+{
+  "name": "will-homelab-dev",
+  "description": "Development marketplace for will-homelab plugin",
+  "owner": {
+    "name": "Will"
+  },
+  "plugins": [
+    {
+      "name": "will-homelab",
+      "description": "Personal assistant and multi-agent system for homelab management",
+      "version": "1.0.0",
+      "source": "./",
+      "author": {
+        "name": "Will"
+      }
+    }
+  ]
+}