docs: Add extension roadmap

- Phase 1-4 migration plan
- Extension points table
- Migration path

Author: KooshaPari

extensions/ROADMAP.md

@@ -0,0 +1,47 @@
+# Extension Roadmap
+
+## Phase 1: Foundation (Current)
+
+- [x] Plugin protocol definition
+- [x] Module contracts
+- [ ] Base loader implementation
+- [ ] Configuration schema
+
+## Phase 2: Core Extensions
+
+- [ ] CLI command extensions
+- [ ] Handler system
+- [ ] Adapter base
+
+## Phase 3: Integration
+
+- [ ] Codex CLI integration
+- [ ] Harbor framework adapters
+- [ ] Portage module system
+
+## Phase 4: Ecosystem
+
+- [ ] Extension registry
+- [ ] Publishing tools
+- [ ] Version compatibility
+
+## Extension Points Summary
+
+| Point | Type | Description |
+|-------|------|-------------|
+| command | CLI | Add new commands |
+| adapter | Integration | Connect external systems |
+| module | Core | Portage modules |
+| renderer | Template | Custom templates |
+| validator | Schema | Input/output validation |
+| middleware | HTTP | Request/response processing |
+| storage | Persistence | Custom backends |
+
+## Migration Path
+
+For existing code:
+1. Identify extension point
+2. Create plugin.yaml
+3. Implement interface
+4. Add tests
+5. Publish to registry