feat: Add granular feature status stages across all skills

Replaces ambiguous 4-status system with 6 clear stages, one per skill:
Planned → Architected → In Progress → In Review → Approved → Deployed

- architecture: sets "Architected" (was "In Progress")
- frontend + backend: explicitly set "In Progress" with checklist items
- qa: sets "In Review" on start, "Approved" on pass (was only "In Review")
- general rules + INDEX.md: updated valid statuses and descriptions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/frontend/SKILL.md

@@ -84,6 +84,10 @@ If no backend needed:
 ## Checklist
 See [checklist.md](checklist.md) for the full implementation checklist.
 
+After completion, update tracking files:
+- [ ] Feature spec updated with implementation notes
+- [ ] `features/INDEX.md` status updated to "In Progress"
+
 ## Git Commit
 ```
 feat(PROJ-X): Implement frontend for [feature name]