The OpenAPI document describes watching a milestone: PUT and DELETE …/milestones/{number}/watch #5315

For: "milestones you can watch move" is reachable from the contract, not only the page and MCP watch.

Done:

• [ ] PUT and DELETE /api/v1/repos/{owner}/{name}/milestones/{number}/watch (src/http/api.ts ~3655) each have a row. The row sits in ROUTES (src/contract/openapi.ts) beside its neighbours, with the request body, each answer and each refusal the handler actually returns; its line(s) leave NOT_YET_DESCRIBED in test/openapi-coverage.test.ts.
• [ ] A test reads both rows and fails without them.

Files: src/contract/openapi.ts, test/openapi-coverage.test.ts, one test file. Risk: #5115 describes the milestone's limb nearby; keep a separate block.