test(runtime-host): bound owned-Host lifecycle tests to kernel contracts

[ggbdpq]

Summary

Fixes #4776 (intermittent owned-Host lifecycle failures). The root-cause analysis and the fix shape are @UncertaintyDeterminesYou4ndMe's, proposed in #4784 and donated to the issue after that PR was withdrawn; this commit implements the test-side fix so the findings are not lost, with small adaptations to the current tree.

Three waits were bounded by numbers the kernel does not promise:

1. Launch-owner exit test gated its assertion on the Client's own connection.closed — the Client aborts that transport after a 2 s unanswered liveness probe, so a merely busy Host resolved it while still running, and the exit budget started at a moment unrelated to shutdown. The assertion now waits on the process directly (waitForProcessExit(pid, 20_000)), a bound derived from the kernel contract: owner loss cannot close a composition before startup settles, and the following shutdown is bounded by shutdownGraceMs (10 s). 20 s sits above every legitimate exit and below the launcher's new 60 s idle grace, so an idle exit cannot satisfy it.
2. The owned-launch fixture ran with idleGraceMs: 10_000, which could expire mid-test and let an idle exit masquerade as an owner-loss exit. It now runs at 60 s with an explicit initialConnectionTimeoutMs: 10_000 so a Candidate no Client ever reaches still exits on its own.
3. "Owned Host exits promptly" conflated shutdown start with shutdown duration, and its 5 s settle bound sat inside the kernel's own 10 s shutdownGraceMs — a starved-but-clean Host was force-terminated and reported false !== true. The test now asserts shutdown start separately (polling the control directory until the registration disappears or reports draining, the state the kernel publishes before any shutdown work) and then settles at 15 s.

Verification

Claim	Command	Result
Focused tests pass with the fix	node --test --test-name-pattern=… on both dist tests (fresh build)	both pass
owned-candidate file complete	node --test owned-candidate.test.js	11 tests, 11 pass, 0 fail
host-kernel file complete	node --test host-kernel.test.js	70 tests: 64 pass, 5 skipped, 1 fail — answers an admitted bootstrap with draining after shutdown commits (EPIPE)
That failure is pre-existing on Windows, not from this diff	control run with the three changed files stashed, rebuilt, same focused test	fails identically on the clean tree
Format	npm run format:check	exit 0

Honest limits: the full Runtime Host suite was also started on this Windows machine and stalled after ~350 tests on a file unrelated to this diff (an environment issue worth its own investigation; the UDS-inspect tests adjacent to the stall are Windows-skipped). The authoritative full-suite result will come from CI on Linux/macOS. The flake itself was reported on macOS arm64; per the issue's data (2/10 and 1/10 focused failures) the tightened bounds remove both timing holes the analysis identified.

AI use

Implemented with ZCode (GLM-5.3-Flash) from @UncertaintyDeterminesYou4ndMe's donated analysis and #4784 patch, adapted to the current tree and re-verified. The commit carries the Generated-by trailer.

Checklist

• Test-only diff; no production code changed
• Analysis credit to the original finder in commit message and PR
• New bounds derived from kernel contracts (shutdownGraceMs, idle grace), not magic numbers
• Pre-existing Windows failures disclosed with control-experiment evidence