feat(events): a failed step may say when to retry (MODULE_API 1.15.0)

A module's perform() may answer { ok: false, retry: true, retryAfterMs }
and the runner waits that long instead of the flat EVENT_STEP_RETRY_MS
(Rust PLAN_REDESIGNS §14.3.13, D371). Dangerous Treasures' warm-up is the
first user.

- dispatch.classify reads it on the retry shape only, clamped to 60 000 to
  1 800 000 ms; a value that is not a number is dropped and logged, and the
  step retries on the flat delay.
- It is one attempt of EVENT_STEP_MAX_ATTEMPTS and degrades the run like any
  retry. A run paused or cancelled in the wait is not picked up.
- Every step.retry log line now carries retryAt (and retryAfterMs when
  hinted); the run console reads "retrying at 20:10".
- MODULE_API 1.15.0, additions only; the engagement manifest is regenerated.
  Module-uo (^1.10.0) answers none of it and is unaffected.
- Test harness: resourcesDb.finishedRunsWithNothingLeft was never stubbed in
  eventRunner.test.js, so a tick that reached the cleanup sweep with a
  terminal run waited on the dead pool.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

server/test/eventModuleContract.test.js

@@ -112,7 +112,7 @@ test('the version a module declares against satisfies ^1.10.0', () => {
   // 1.10.0 loading — Module-uo declares exactly `^1.10.0` — and this is the
   // assertion that says it does. The number itself is pinned in version.js.
   assert.ok(semver.satisfies(MODULE_API_VERSION, '^1.10.0'), MODULE_API_VERSION)
-  assert.equal(MODULE_API_VERSION, '1.14.0')
+  assert.equal(MODULE_API_VERSION, '1.15.0')
 })
 
 test('a module registers actions, budgets, leases and option sources', () => {