fix: skip the redundant simulator list after a boot this run performed

[janicduplessis]

Description

On a run that creates a simulator, ensureOwnedIosDevice boots it with a blocking simctl bootstatus -b and then ensureIosBooted opens with resolveOwnedIosSim(udid) -> listAllIosSims() -> xcrun simctl list devices --json, purely to learn a state it already knows. The sim is Booted, so the function returns on the next line -- but that list is the first simctl call after a boot, and CoreSimulator is still busy for several seconds after bootstatus claims the boot is done. Measured on this machine: simctl list devices --json costs 7.9 s right after a boot versus 0.06 s on a quiet one, and the device ... booted phase line reported 12.3 s / 8.7 s / 2.0 s across the three cache-hit baselines in investigations/2026-09-02-cache-hit-run-time.md (mean total 72.6 s).

Ownership is not weakened: ensureOwnedIosDevice already re-resolved the sim by name (resolveOwnedIosSim, or createOwnedIosSim for one it just made) earlier in the same call chain, so invariant 2 is satisfied before anything boots.

Solution

ensureOwnedIosDevice now reports the udid it booted on the record it returns (bootedUdid), and ensureIosBooted returns { ok: true, udid } immediately when that udid is the one it was asked about. It is deliberately narrow: the field is set only where this call actually ran bootIosSim -- the created path and the reuse path that found the sim shut down. A reused sim that was already Booted carries no bootedUdid, so it is still listed, because nothing in this process proves it did not shut down in between. A bootedUdid for a different sim does not vouch for this one either.

bootedUdid is attached after configureOwnedIosSim has written the registry, alongside created/deviceType/runtime, so it is never persisted -- it means "this process booted it", and it would be a lie in the next one.

I used the udid rather than the whole IosSimRecord the issue suggests: on the created path there is no IosSimRecord to return (createOwnedIosSim returns a name and a udid, not a simctl list row), and the udid match is the entire decision.

No tool call changes, so invariant 9 needs nothing new here; the argument lists are untouched and one simctl list devices --json is simply not issued.

Test plan

• engine-device.test.ts: ensureBooted issues zero commands when the record carries a matching bootedUdid; it still lists for a reused sim with no bootedUdid, and for a bootedUdid that names another sim. ensureOwnedDevice reports the boot it performed on the created path and on the reuse-after-shutdown path, reports nothing on the already-booted path, and the persisted registry record is unchanged ({ deviceUdid, owned, deviceName }).
• ios-command.test.ts: an end-to-end run wired to the real ensureBooted with a fake clock that charges 8 s per simctl list devices -- the phase line reads booted (0ms) on the fresh-boot path and booted (8s) on the path that has to list. Ablation: dropping the new early return in ensureIosBooted fails both this test and the engine one.
• pnpm run format:check, lint, build, typecheck, pnpm test (83 files, 3336 tests), pnpm run knip all pass on this branch.

Fixes #268