- create_simulation: name falls back to template.name when template_id provided
and name is absent/empty (AC-27.1)
- templates POST/PATCH: isinstance(list) check on technique_ids/tactic_ids
before resolving, returns 400 with clear message
- 5 new tests: unknown technique_id → 400 (POST+PATCH), unknown tactic_id → 400
(POST+PATCH), name fallback to template.name
- mypy: merged template branch into if/else to eliminate union-attr false positives
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>