The OpenAPI document describes the forge's front reads: health, here, front, forge and contribute #5039

Intent: a harness that lands on a forge learns where it is and how it is from the OpenAPI document.

Done:

• [ ] src/contract/openapi.ts has a row for GET /api/v1/health, GET /api/v1/here, GET /api/v1/front, GET /api/v1/forge and GET /api/v1/contribute, each with auth, the body and query fields its handler reads, its success status when not 200, and the refusals it answers by stable error code
• [ ] each summary says the answer's shape exactly as the handler answers it today
• [ ] test/openapi.test.ts still passes, and a new test asserts each new path and method is in the served document (GET /contract/openapi.json)

Files: src/contract/openapi.ts, one new test. Other issues add OpenAPI rows in parallel: add these as one block after the last ${REPO} row and before /mcp, and change no other row. Do not change any route.