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/README.md

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+# GA Agent Project
+
+Build workspace for Google Analytics tools and the `15-ourdigital-ga-agent` Claude Skill.
+
+## Architecture
+
+```
+┌─────────────────────────────────────────────────────────────┐
+│                     Infrastructure                           │
+│  ┌──────────────┐  ┌──────────────┐  ┌──────────────────┐   │
+│  │ GA4 MCP      │  │ BigQuery MCP │  │ Dimension Explorer│   │
+│  └──────────────┘  └──────────────┘  └──────────────────┘   │
+└─────────────────────────────────────────────────────────────┘
+                              │
+┌─────────────────────────────────────────────────────────────┐
+│  15-ourdigital-ga-agent (Claude Skill)                       │
+│  • Interactive analysis • Reports • Period comparisons       │
+└─────────────────────────────────────────────────────────────┘
+                              │
+┌─────────────────────────────────────────────────────────────┐
+│                  Standalone Services                         │
+│  ┌────────────────────┐  ┌────────────────────────────┐     │
+│  │ Slack Reporter     │  │ Realtime Watcher (deferred)│     │
+│  └────────────────────┘  └────────────────────────────┘     │
+└─────────────────────────────────────────────────────────────┘
+```
+
+## Components
+
+| # | Component | Type | Priority | Status |
+|---|-----------|------|----------|--------|
+| 1 | [MCP Setup](01-mcp-setup/) | Infrastructure | P0 | Pending |
+| 2 | [GA Agent Skill](02-ga-agent-skill/) | Claude Skill | P0 | Pending |
+| 3 | [Dimension Explorer](03-dimension-explorer/) | Utility | P1 | Pending |
+| 4 | [Slack Reporter](04-slack-reporter/) | Service | P2 | Pending |
+| 5 | [Realtime Watcher](05-realtime-watcher/) | Service | P3 | Deferred |
+
+## Build Order
+
+```
+Phase 1: Foundation
+├── [1] MCP Setup ←── START HERE
+└── [2] GA Agent Skill
+
+Phase 2: Enhancements
+├── [3] Dimension Explorer
+└── [4] Slack Reporter
+
+Phase 3: Advanced
+└── [5] Realtime Watcher (deferred)
+```
+
+## Project Structure
+
+```
+ga-agent-project/
+├── README.md
+├── .gitignore
+├── config/                    # Credentials (gitignored)
+├── docs/
+│   ├── PROJECT-PLAN.md        # Full implementation plan
+│   ├── 01-mcp-servers-overview.md
+│   ├── 02-setup-guide.md
+│   └── 03-visualization-setup.md
+├── 01-mcp-setup/              # MCP server installation
+├── 02-ga-agent-skill/         # Core Claude Skill
+├── 03-dimension-explorer/     # Dimension/metric validator
+├── 04-slack-reporter/         # Automated Slack reports
+└── 05-realtime-watcher/       # Real-time monitoring (deferred)
+```
+
+## Quick Resume
+
+```bash
+cd /Users/ourdigital/Projects/claude-skills-factory/ga-agent-project
+
+# Read the full plan
+cat docs/PROJECT-PLAN.md
+
+# Start with Component 1
+cat 01-mcp-setup/README.md
+```
+
+## Prerequisites
+
+- Google Cloud account with billing enabled
+- GA4 property access (Admin or Viewer)
+- Python 3.10+
+- Node.js 18+ (for BigQuery MCP)
+- Slack workspace (for Component 4)