Initialize project skeleton with CLI and documentation

Add initial project structure including:
- Go module with Cobra CLI dependency
- Root command and main entrypoint
- Basic documentation (README, AGENTS.md, architecture, decisions,
  development, roadmap)
- Configuration example and gitignore
- Tool version management with mise
- Comprehensive project rules and conventions

docs/README.md

@@ -0,0 +1,8 @@
+# Docs
+
+| File | Content |
+|------|---------|
+| `architecture.md` | Module layout, package boundaries |
+| `decisions.md` | Technical decisions (ADR) |
+| `roadmap.md` | Feature progress and status |
+| `development.md` | Build, test, debug workflow |