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>

features/INDEX.md

@@ -3,10 +3,12 @@
 > Central tracking for all features. Updated by skills automatically.
 
 ## Status Legend
-- **Planned** - Requirements written, ready for development
-- **In Progress** - Currently being built
-- **In Review** - QA testing in progress
-- **Deployed** - Live in production
+- **Planned** - `/requirements` done, spec written, architecture not yet designed
+- **Architected** - `/architecture` done, tech design approved, ready to build
+- **In Progress** - `/frontend` or `/backend` active or completed, not yet in QA
+- **In Review** - `/qa` active, testing in progress
+- **Approved** - `/qa` passed, no critical/high bugs, ready to deploy
+- **Deployed** - `/deploy` done, live in production
 
 ## Features