Remove the proof step: with check.run lint and types only, it proves nothing the merge queue's gate does not #7779

Part of #7703 (one path: check, review, land, live). Since 2026-11-01 forge.json check.run is lint and types only, so the proof before the line (#7616) runs the same command the merge queue's gate runs a minute later on nearly the same tree. Delete it: the proof run, its ledger row, its queue admission rule, proofWords in the next-actor line, and its tests. Do not rename it; remove it.

Done when: no pull waits on a proof; the pull page and MCP pull never mention one; bun test covers that an approved green pull joins the merge queue with no proof run.

Files: src/checks/proof.ts, src/checks/service.ts, src/checks/queue.ts, src/flow/next_actor.ts, src/core/proof_runs.ts

Parked by the crew: the check stayed red through 2 automatic tries (pull #8251 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.