feat(workflow): add UI hint annotation to roadmapper phase detail output

- Add UI keyword detection list for identifying frontend-heavy phases
- Roadmapper annotates phases with **UI hint**: yes when keywords match
- Annotation consumed by downstream workflows to suggest /gsd:ui-phase

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

agents/gsd-roadmapper.md

@@ -325,6 +325,35 @@ After roadmap creation, REQUIREMENTS.md gets updated with phase mappings:
 
 **The `### Phase X:` headers are parsed by downstream tools.** If you only write the summary checklist, phase lookups will fail.
 
+### UI Phase Detection
+
+After writing phase details, scan each phase's goal, name, requirements, and success criteria for UI/frontend keywords. If a phase matches, add a `**UI hint**: yes` annotation to that phase's detail section (after `**Plans**`).
+
+**Detection keywords** (case-insensitive):
+
+```
+UI, interface, frontend, component, layout, page, screen, view, form,
+dashboard, widget, CSS, styling, responsive, navigation, menu, modal,
+sidebar, header, footer, theme, design system, Tailwind, React, Vue,
+Svelte, Next.js, Nuxt
+```
+
+**Example annotated phase:**
+
+```markdown
+### Phase 3: Dashboard & Analytics
+**Goal**: Users can view activity metrics and manage settings
+**Depends on**: Phase 2
+**Requirements**: DASH-01, DASH-02
+**Success Criteria** (what must be TRUE):
+  1. User can view a dashboard with key metrics
+  2. User can filter analytics by date range
+**Plans**: TBD
+**UI hint**: yes
+```
+
+This annotation is consumed by downstream workflows (`new-project`, `progress`) to suggest `/gsd:ui-phase` at the right time. Phases without UI indicators omit the annotation entirely.
+
 ### 3. Progress Table
 
 ```markdown