fix: workload promote test and status code

[dimakis]

Summary

• Fix vacuous broadcast test: setWorkloadBroadcast() instead of monkey-patching non-existent app._workloadBroadcast
• Add missing test for promote with description but no title
• Return 400 (not 404) when item exists but has no title

Pre-existing issues flagged by Centaur on PR #428.

Test plan

• workload-routes tests pass (25/25)

🤖 Generated with Claude Code

[dimakis]

Centaur Review

Found 2 issue(s) (1 warning).

server/__tests__/workload-routes.test.ts

Good fixes — proper use of setWorkloadBroadcast API and correct 400/404 status differentiation — but the new 400 branch (item exists, no title) lacks test coverage.

• 🟡 missing_tests: The code change introduces a new 400 status path (item exists in workloadStore but has no title), but there's no test covering it. The new test only covers the 404 path (missing item). Add a test that creates an item with an empty-string title, then promotes it without providing a body title, and asserts 400 with 'No title provided'. [fixable]
• 🔵 style (L570): The reset comment '// Reset — no broadcast callback in test environment' explains what the line does, not why. The code setWorkloadBroadcast(() => {}) is self-explanatory. Per project conventions, this comment should be removed. [fixable]

[dimakis]

🔵 style: The reset comment '// Reset — no broadcast callback in test environment' explains what the line does, not why. The code setWorkloadBroadcast(() => {}) is self-explanatory. Per project conventions, this comment should be removed. [fixable]