* fix(sandbox): measure warm-pool idle age on a monotonic clock
Warm-pool expiry measures a duration, but every provider stamped and reaped
entries using the wall clock. A forward correction could therefore destroy
fresh sandboxes, while a backward correction could retain expired ones until
the clock caught up.
Move every warm-pool writer and reader to time.monotonic(), including the
Tenki and OpenSandbox reset paths missed by the earlier closed attempt. Keep
absolute SandboxInfo.created_at and reconciliation grace timestamps on the
wall clock. Convert AIO's sibling active-idle timestamps as one clock domain,
and update finite clock mocks for the additional duration read.
Fixes#6970
* test(sandbox): keep active-idle race fixtures in the monotonic domain
The production AIO activity clock moved to monotonic time, but the shared
orphan-reconciliation helper still stamped active fixtures with wall time.
CI then computed a negative idle age, so two teardown race tests never reached
the ownership gate. Use the same monotonic domain as production.
* test(sandbox): read warm-pool idle fixtures on the monotonic clock
The idle-age conversion left several fixtures seeding the fields the reaper
now reads with values from the clock it no longer reads:
- `test_idle_reaping_forces_a_new_remote` froze `warm_pool_lifecycle.time.time`,
so the benchmark's reaper compared against real elapsed monotonic seconds —
zero over the test's lifetime. Nothing expired, the entry survived, and the
second turn came back as a warm hit.
- Three orphan-reconciliation fixtures seeded `_last_activity` with `0.0` and
two aio fixtures with `time.time()`, both of which are far below a running
monotonic clock: the computed idle age went negative, so the reaper never
reached the ownership claim these tests are built to exercise.
Seed them from `time.monotonic()` instead, and keep `created_at` (a wall-clock
field) on `time.time()`.
