fix(pool): harden cancellation, CI registration, and log safety

Address review findings on the persistent runner pool:

- Register the new runner/pool unit suites in test:ci:unit so CI
  exercises them (they were missing from the script).
- Stop logging the raw request on invalid input: the request body
  includes the prompt, which must not be written to logs. Log field
  presence and the request id instead.
- Reject and error in-flight requests when a runner is evicted, so
  their callers resolve instead of hanging. A plain clear() dropped
  their terminal events.
- Give the mock fixture a 60s safety net (unref'd) so slow CI does not
  let it exit before the test cancels the request.
- Assert the queueing precondition (r1 started) before canceling r2 in
  the demux test.