fix(core): honest close-path state when eviction cancels pending questions

[thiago-carneiro]

Issue for this PR

Closes #52599

Type of change

• Bug fix

What does this PR do?

When a location closes and cancels pending questions, the cancellation carries no reason: the form state is a bare { status: "cancelled" }, and the tool failure reported to the model never names the pending question. The branch builds on #52587, which fixed the tool-part message; this PR covers the close path.

I pass an eviction cause through the close path: pending forms cancelled by an eviction close now carry cause: "evicted" and a message naming the pending question. The cancelled form state now has an optional cause field, and I regenerated the API clients. In the tool failure reported back to the model, a question cancelled while waiting now names the pending question instead of using the generic close message; user dismissals keep the same wording, now also naming the question. Non-eviction closes (reload, debug) still cancel without a cause — their form state stays bare.

Implementation note: with no borrowers the entry's scope closes synchronously inside the invalidate call, so the cause-carrying cancel runs in a narrow hook just before it — non-eviction invalidations are untouched.

I did not change the eviction policy or the 60-minute deadline; those are #51343's questions. Restoring pending forms across reconnects (#44471) stays out of scope.

How did you verify your code works?

• bun run test in packages/core: full suite passes (5628 tests, 0 failing), including 7 new tests covering the eviction-cancelled form state and the tool-failure message
• bun turbo typecheck and bunx oxlint pass
• bun run check passes

The new tests cover the behavior. To see it manually, leave a question form pending in an idle session until eviction — the cancelled form then names the eviction and the pending question.

Screenshots / recordings

Not a UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

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