Phase 3 — rebind both ticker call sites to resolve_cron_scheduler(). Default
(built-in) path is byte-identical; Phase 0 characterization tests + the full
gateway suite (6919) stay green.
Task 3.1: split gateway/run.py _start_cron_ticker into:
- _start_gateway_housekeeping() — the gateway-only chores (channel-dir
refresh, image/doc cache cleanup, paste sweep, curator poll), now on their
own loop/thread, independent of which cron provider is active.
- _start_cron_ticker() — kept as a DEPRECATED shim that runs only the
built-in InProcessCronScheduler().start(), preserving the symbol for
hermes_cli/debug.py and the Phase 0 characterization test.
Task 3.2: start_gateway() resolves the provider and runs provider.start() in
the 'cron-scheduler' thread, plus a second 'gateway-housekeeping' thread;
teardown sets the shared cron_stop, calls provider.stop(), joins both.
Task 3.3: desktop _start_desktop_cron_ticker() swapped its inline tick loop for
resolve_cron_scheduler().start() (no adapters/loop — desktop has none).
The provider owns ONLY the cron tick (so an external scale-to-zero provider
with no 60s loop fits); gateway housekeeping is decoupled from the cron
trigger. Both threads share cron_stop.
Verified: full tests/cron/ (453) + full tests/gateway/ (6919) green. Manual
gateway smoke (Task 3.4) is operator-run, pending.
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