docs: initialize project and codebase maps

- Finalized PROJECT.md incorporating 'Zero-Pollution' constraints
- Enforced native Git portability (git pull sync only)
- Generated ARCHITECTURE.md and STACK.md maps
- Deleted .agent/skills/.gitignore to physically track flattened skills

.planning/codebase/STACK.md

@@ -0,0 +1,7 @@
+# Tech Stack
+
+- **CLI/Execution**: Node.js (v18+)
+- **Agent Memory**: SQLite (via `claude-mem` MCP)
+- **Design Tokens**: Python (via `ui-ux-pro-max-skill`)
+- **Version Control**: Git / Git Worktrees
+- **Documentation**: Obsidian Flavored Markdown (OFM)