test(platform/handlers): add comprehensive instructions_test.go — 36 cases
Covers all CRUD endpoints + resolve:
- List: empty, workspace filter, scope filter, no params, DB error
- Create: success, missing scope/title/content, invalid scope, workspace scope edge cases, content/title length limits, DB error
- Update: success, all fields, not found, length limits, exec error, empty body (WithArgs ordering fix)
- Delete: success, not found, exec error
- Resolve: empty, workspace only, global only, both scopes, scope transition (consecutive globals share header), query error, missing workspace ID, scan error continues
- Scan helper: scan error continues
Branch: feat/instructions-test-coverage (PR #679)
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>