feat(openapi): document validate-linked-issue + check-before-start

[philluiz2323]

What

POST /v1/repos/:owner/:repo/validate-linked-issue and POST /v1/repos/:owner/:repo/check-before-start are live with MCP tools (loopover_validate_linked_issue / loopover_check_before_start) and Zod output shapes, but were missing from the OpenAPI contract — the same class of gap #6611 fixed for gate-config/effective.

Change

• Add request + response schemas in src/openapi/schemas.ts from the MCP tool shapes
• Register both schemas and registerPath entries in src/openapi/spec.ts
• Assert paths + schema keys in test/unit/openapi.test.ts
• Regenerate apps/loopover-ui/public/openapi.json

Closes #9304

Made with Cursor

[philluiz2323]

Closing to avoid openapi.json conflict with #9405 (same generated artifact). Will reopen #9304 after #9405 merges, or replace this slot with a non-conflicting issue.

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.59%. Comparing base (b4064b6) to head (3df6a7b).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9406      +/-   ##
==========================================
+ Coverage   75.46%   75.59%   +0.13%     
==========================================
  Files         275      277       +2     
  Lines       58030    58364     +334     
  Branches     6199     6206       +7     
==========================================
+ Hits        43790    44123     +333     
  Misses      13970    13970              
- Partials      270      271       +1     

Flag	Coverage Δ
backend	99.70% <100.00%> (?)

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Files with missing lines	Coverage Δ
src/openapi/schemas.ts	100.00% <100.00%> (ø)
src/openapi/spec.ts	99.50% <100.00%> (ø)