refactor: Migrate to Git-based workflow (v1.4.0)

BREAKING CHANGE: Removed FEATURE_CHANGELOG.md and test-reports/

**What changed:**
- All 6 agents now use Git commands to check existing features/components
- Feature specs include test results and deployment status (no separate files)
- Git commits are the single source of truth for implementation details
- Git tags for deployment versioning (e.g., v1.0.0-PROJ-1)

**Why:**
- Prevents context bloat (no growing FEATURE_CHANGELOG.md)
- Scales better (Git is built for large projects)
- No manual changelog maintenance
- Better developer experience (native Git workflow)

**Migration:**
- Requirements Engineer: Uses `ls features/` and `git ls-files` instead of FEATURE_CHANGELOG
- Solution Architect: Uses `git ls-files src/components/` to check existing code
- Frontend/Backend Devs: Use `git log --grep="PROJ-X"` to see feature history
- QA Engineer: Adds test results directly to feature spec
- DevOps: Updates feature spec with deployment status + creates Git tags

**Files changed:**
- Updated all 6 agent instructions (.claude/agents/*.md)
- Deleted FEATURE_CHANGELOG.md
- Deleted test-reports/ folder
- Updated PROJECT_CONTEXT.md (removed references)
- Updated README.md (v1.4.0, updated workflow)
- Updated features/README.md (new format with QA + Deployment sections)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

PROJECT_CONTEXT.md

@@ -139,8 +139,6 @@ ai-coding-starter-kit/
 │   └── agents/              ← 6 AI Agents (Requirements, Architect, Frontend, Backend, QA, DevOps)
 ├── features/                ← Feature Specs (Requirements Engineer creates these)
 │   └── README.md            ← Documentation on how to write feature specs
-├── test-reports/            ← QA Test Reports (QA Engineer creates these)
-│   └── README.md            ← Documentation on test report format
 ├── src/
 │   ├── app/                 ← Pages (Next.js App Router)
 │   ├── components/          ← React Components
@@ -150,7 +148,6 @@ ai-coding-starter-kit/
 │       └── utils.ts         ← Helper functions
 ├── public/                  ← Static files
 ├── PROJECT_CONTEXT.md       ← This file - update as project grows
-├── FEATURE_CHANGELOG.md     ← Tracks all implemented features
 └── package.json
 ```
 
@@ -193,9 +190,10 @@ ai-coding-starter-kit/
    - Requirements → Architecture → Development → QA → Deployment
    - Each agent knows when to hand off to the next agent
 
-4. **Update documentation as you go**
-   - `PROJECT_CONTEXT.md` - Add features to roadmap, mark them as done
-   - `FEATURE_CHANGELOG.md` - Automatically updated after deployment
+4. **Track progress via Git**
+   - Feature specs in `/features/PROJ-X.md` show status (Planned → In Progress → Deployed)
+   - Git commits track all implementation details
+   - Use `git log --grep="PROJ-X"` to see feature history
 
 ---