Sentinel: shared:01m23vygyffx5hg2f5vm8r74sr:2tcvuk57nu was degraded 34 minutes today: trevato/forge: "the merge queue > a gate that never answers is abandoned at the deadline, and the next sweep lands (#34… #5737

This pull makes a small hardening change to the "a gate that never answers is abandoned at the deadline" test. I can't show it fixes the flake, because I could not reproduce one.

• What I found: the test passed on every run here. Earlier pulls (#5357, #5627, #5699) already fixed the likely cause, a slow check machine hitting the default 5s test timeout. The last of those, #5699, gave the test the 300s SLOW timeout at 10:21. This sentinel report came at 11:13, so it may still be counting failures from before that fix. The issue carries no failure log, so I could not confirm that.
• What changed: test/merge-queue.test.ts now keeps every deadline armed through gateDeadlineForTest and fires all of them when the gate is reached, instead of keeping only the last. A gate left over from another test could otherwise take over the hand-fired deadline and leave the real one unfired.
• What I left out: no change to src/checks/queue.ts, since the queue's behaviour is correct.
• Try it: bun test test/merge-queue.test.ts gives 16 pass, and the type check is clean.
• What to watch: if shared:…2tcvuk57nu shows up as degraded again after this lands, the check log from that failure is the next thing to read.

Closes #5734

This pull makes a small hardening change to the "a gate that never answers is abandoned at the deadline" test. I can't show it fixes the flake, because I could not reproduce one.

• What I found: the test passed on every run here. Earlier pulls (#5357, #5627, #5699) already fixed the likely cause, a slow check machine hitting the default 5s test timeout. The last of those, #5699, gave the test the 300s SLOW timeout at 10:21. This sentinel report came at 11:13, so it may still be counting failures from before that fix. The issue carries no failure log, so I could not confirm that.
• What changed: test/merge-queue.test.ts now keeps every deadline armed through gateDeadlineForTest and fires all of them when the gate is reached, instead of keeping only the last. A gate left over from another test could otherwise take over the hand-fired deadline and leave the real one unfired.
• What I left out: no change to src/checks/queue.ts, since the queue's behaviour is correct.
• Try it: bun test test/merge-queue.test.ts gives 16 pass, and the type check is clean.
• What to watch: if shared:…2tcvuk57nu shows up as degraded again after this lands, the check log from that failure is the next thing to read.