Emphasize Docker build and container startup verification in workflow

Updated general-dev-workflow skill to stress that for Docker projects,
BOTH build success AND successful container startup are required before
considering a change complete.

Key additions:
- Docker container startup verification is mandatory, not optional
- Containers must have status 'Up', not 'Restarting' or 'Exited'
- Check container logs for errors during startup
- Missing config files, invalid env vars, DB issues only show at runtime
- Startup failures block production deployments
- Updated Phase 4 checkpoint to include container startup validation

Lesson from email-api issue: missing appsettings.json caused restart loop
that had no visible logs during build. This must be caught in Phase 4
before code review and prevents production issues.

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

docs/skills/general-dev-workflow.md

@@ -85,11 +85,24 @@ Steps:
 - **Docker projects**: Run `docker compose --build` to verify all Docker images build successfully
 - Check build artifacts exist and are correct size (no suspiciously small binaries)
 
-**Why build verification matters:**
+**Docker container startup verification (required for Docker projects):**
+- After successful build, run `docker compose up -d` to start all containers
+- **Wait 10-15 seconds** for services to initialize (database migrations, seeding, etc.)
+- Run `docker compose ps` and verify all containers have status **Up** (not Restarting or Exited)
+- Run `docker logs <service>` for each container and verify:
+  - No errors or fatal exceptions in startup logs
+  - Services logged successful initialization (e.g., "startup complete", "listening for requests")
+  - Database migrations completed successfully (if applicable)
+  - Configuration loaded without errors
+- **This is not optional for Docker changes** — a container that restarts means the change is incomplete
+- If any container fails to start, the build is not successful until fixed
+
+**Why build AND startup verification matters:**
 - Catches missing dependencies, import errors, and configuration issues early
-- Prevents "it works on my machine" problems during code review
-- Docker builds especially must be verified as they catch missing project references and file copies
-- A failed build blocks reviewers and CI/CD pipelines
+- Docker builds catch missing project references and file copies, but don't catch runtime config problems
+- Missing appsettings files, invalid environment variables, or database connection issues only show up at runtime
+- A failed startup blocks entire services in production — this must be caught before code review
+- A failed build blocks reviewers and CI/CD pipelines; a failed startup blocks production deployments
 
 **Write tests for your changes:**
 - Unit tests for individual functions/methods
@@ -112,9 +125,9 @@ Steps:
 - Any manual testing notes
 - Known limitations or edge cases not yet tested
 
-**Output**: Passing tests, code coverage report, test summary, successful build.
+**Output**: Passing tests, code coverage report, test summary, successful build, containers running successfully (for Docker projects).
 
-**Checkpoint**: Does the code compile without errors? Can you confidently say the code works? Are there any untested paths you're worried about?
+**Checkpoint**: Does the code compile without errors? Do all Docker containers start and stay running (status: Up)? No errors in container logs? Can you confidently say the code works? Are there any untested paths you're worried about?
 
 ---
 
@@ -197,7 +210,7 @@ Problem it solves / value it adds (2-3 sentences)
 
 **Keep phases focused.** Don't mix planning with implementation. Don't test in Phase 2. This separation helps catch problems early.
 
-**Verify builds before review.** Always run a full build (`dotnet build` or `docker compose --build`) in Phase 4 before opening the PR. Build errors block reviewers and waste CI/CD time. If you're changing Dockerfiles or project dependencies, this is especially critical.
+**Verify builds AND container startup before review.** Always run a full build (`dotnet build` or `docker compose --build`) in Phase 4 before opening the PR. **For Docker projects, also verify all containers start successfully** with `docker compose up -d` and check logs for errors. Build errors block reviewers; startup failures block deployments. Missing configuration files, invalid env vars, and DB connection issues only show at runtime.
 
 **Commit frequently.** Small commits are easier to review, easier to revert if needed, and easier to understand. Aim for 50-200 lines per commit.