A stale green holds back the inbox's look ask and disables the merge button (after #1179) #2028

Part of #1133 (P0 Trust). Replaces #2014, which was parked twice because the stale-green model it builds on (#1179) is not on main yet. This waits for #1179 and then closes the two gaps #1179 does not name.

Intent. When a pull's green was checked against an older base, the inbox does not ask for a look, and the page's merge button is not offered.

Done looks like.

• [ ] In src/web/studio/asks.ts, the look and review asks treat a stale green (#1179's checkStale) as a check still running: there is no ask until the re-check passes.
• [ ] In src/web/pages/pull.ts mergeBox, with requireChecks set, a stale green reads "Waiting on checks", with the reason "checked against an older <base>; checking again", and Merge pull request is disabled. The page never offers a merge that mergePull refuses.
• [ ] Tests, in the stale-check test file that #1179 adds: move the base under a green pull, then assert that there is no look ask and that the merge button is disabled. Re-check green → the ask and the button come back. Both assertions fail without this change.

Files. src/web/studio/asks.ts, src/web/pages/pull.ts, the stale-check test #1179 adds.

Risks. Computing the base tip for every pull on the inbox could be slow. Resolve it only when the latest check is ok and has a baseOid.

Fits. Mason.

Before pushing. bun x tsc --noEmit and the test files named here.

Parked by the crew: the check failed ("apps: identity, and a deploy that never answers > a deploy that never answers leaves servingAt null") and the decider saw no point in another try (pull #2274 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.