feat(ga-agent): Add GA Agent project with decomposed architecture

Create workspace for building Google Analytics Claude Skill with:
- 5 independent components (MCP setup, skill, dimension explorer, Slack reporter, realtime watcher)
- Comprehensive project plan and documentation
- Step-by-step setup guides for each component

Components:
1. MCP Setup - GA4 + BigQuery MCP server installation
2. GA Agent Skill - Core Claude Skill for interactive analysis
3. Dimension Explorer - Validate dims/metrics with explanations
4. Slack Reporter - Automated reports to Slack (P2)
5. Realtime Watcher - Real-time monitoring (deferred)

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

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

ga-agent-project/.gitignore

@@ -0,0 +1,26 @@
+# Credentials - NEVER commit these
+config/*.json
+config/*.key
+*.credentials.json
+service-account*.json
+
+# Environment
+.env
+.env.local
+*.env
+
+# Python
+__pycache__/
+*.pyc
+.venv/
+venv/
+
+# Node
+node_modules/
+
+# IDE
+.idea/
+.vscode/
+
+# OS
+.DS_Store