feat: add ui_design_specialist (Phase 3 UI Design) v0.2.0

- New specialist: ui_design_specialist with iterative mockup dialog
- New Phase 3 (UI Design) between Architecture and Implementation
- Relay model: orchestrator passes responses verbatim in Phase 3
- Cost-control exception for UI Design phase (unlimited subagent calls)
- Webspace mockup workflow with cache-buster and obscure dirs
- UX states coverage (loading, empty, error, partial)
- WCAG 2.1 AA accessibility guidelines
- Design tokens (CSS custom properties) in design system
- Component states (hover, focus, active, disabled, loading, error)
- Sitemap/wireframe before mockups for complex UIs
- Real content strategy (no Lorem Ipsum)
- Form validation UX in mockups
- Dark mode and i18n support (optional)
- Design handoff support (specialist available during implementation)
- Skip mechanism for non-UI projects
- Mockup state file for context compression recovery
- Multi-page mockup strategy with index.html
- task_graph.json mockup references
- Plugin version: 0.1.14 -> 0.2.0
- 47 files changed across 7 implementation blocks
- 3 review rounds with 41 corrections integrated

helpers/handover_protocol.py

@@ -47,6 +47,7 @@ KNOWN_SPECIALISTS = {
     "solution_architect",
     "test_debug_engineer",
     "hacker",
+    "ui_design_specialist",
 }
 
 # Hard caps (token budget). All numbers are conservative defaults that match