Engine (packages/engine):
- New checkDuplicateAssignment() pure function: detects same resource
assigned to same project with overlapping dates
- 15 unit tests covering: overlap, no-overlap, cancelled, self-exclude,
string dates, PROPOSED status
Application layer (packages/application):
- createAssignment: throws CONFLICT before DB write if duplicate found
- fillDemandRequirement: same check before entering transaction
AI Assistant (packages/api/router/assistant-tools.ts):
- create_allocation: checks before creating, returns helpful error message
- fill_demand: same check using demand's projectId
UI (apps/web):
- AllocationModal: amber warning when resource already assigned to
selected project with overlapping dates (non-blocking)
Database cleanup:
- Found and merged 1 duplicate: Wong Wong on Porsche Taycan Sport Film
(2 overlapping PROPOSED assignments merged into 1)
Regression: 298 engine tests pass (283 + 15 new). TypeScript clean.
Co-Authored-By: claude-flow <ruv@ruv.net>