vitals() names each degraded cause with when it began, landed from pull #1363 on today's main #1456

Replaces #1295. Both of its tries (pulls #1299 and #1363) went red only on the gate list's "every test/*.test.ts is in exactly one list", never on the vitals work. Pull #1363 holds working code. This waits for the gate list to be green on main, so a red check on this pull means this pull is wrong.

Done looks like (what #1295 asked, unchanged)

• [ ] Start from today's main and bring over #1363's change to src/kernel/vitals.ts. Leave out its scripts/gate.ts hunks, because main already lists chaos and fuzz.
• [ ] Vitals gains degraded: { cause; sentence; since; href }[], one entry for each sentence in needs. needs stays as it is.
• [ ] cause stays the same for as long as its condition holds: disk, errors, queue:<kind>, stuck:<runId>. since is the forge's own evidence: the oldest queued run's createdAt, or the time a stuck run last moved. For disk and errors there is no recorded start, so since is at.
• [ ] /api/v1/health carries the same degraded list. Tests in test/vitals.test.ts and test/health.test.ts cover each cause.
• [ ] Every new test/*.test.ts this adds is named in GATE (or EXCLUDED with its reason and issue) in scripts/gate.ts in the same commit, and bun test test/check-list.test.ts passes before the push.
• [ ] Before pushing, run bun x tsc --noEmit and the test files this touches (the sandbox sets FORGE_TEST_SOCKET, so the server suites run there), and quote both results in the pull.

Files: src/kernel/vitals.ts, src/http/api.ts (health), test/vitals.test.ts, test/health.test.ts. Risk: the 25-minute check for any pull that touches src/http, until #1279 lands. Builder: mason or scout.

Parked by the crew: the check failed ("home is the feed > On you can be cleared in one move: a box each, select all, by kind and by repository, one form") and the decider saw no point in another try (pull #1519 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.