docs(workflow): enforce stack verification as mandatory step

- Added "Stack Verification" section to CLAUDE.md with detailed steps.
- Updated WORKFLOW.md to mandate running the full stack before marking work as complete.
- Prevents issues where high test coverage masks application startup failures.

CLAUDE.md

@@ -83,6 +83,37 @@ docs/
 3. **Testing Required**: All code must be tested, aim for >90% coverage
 4. **Code Review**: Must pass multi-agent review before merge
 5. **No Direct Commits**: Never commit directly to `main` or `dev`
+6. **Stack Verification**: ALWAYS run the full stack before considering work done (see below)
+
+### CRITICAL: Stack Verification Before Merge
+
+**This is NON-NEGOTIABLE. A feature with 100% test coverage that crashes on startup is WORTHLESS.**
+
+Before considering ANY issue complete:
+
+```bash
+# 1. Start the dev stack
+make dev
+
+# 2. Wait for backend to be healthy, check logs
+docker compose -f docker-compose.dev.yml logs backend --tail=100
+
+# 3. Start frontend
+cd frontend && npm run dev
+
+# 4. Verify both are running without errors
+```
+
+**The issue is NOT done if:**
+- Backend crashes on startup (import errors, missing dependencies)
+- Frontend fails to compile or render
+- Health checks fail
+- Any error appears in logs
+
+**Why this matters:**
+- Tests run in isolation and may pass despite broken imports
+- Docker builds cache layers and may hide dependency issues
+- A single `ModuleNotFoundError` renders all test coverage meaningless
 
 ### Common Commands