Shorten update-check interval and add foreground/network triggers

[MaplumeX]

Summary

Update checks previously ran on a 24-hour wall-clock cadence, so a compatible hub upgrade could go unnoticed for a day, and server switches relied on the startup check plus the 426 trigger. This change tightens the cadence and wires the checks into the events that actually signal "something changed": server switches, returning to the foreground, and network recovery.

Changes

Scheduling (packages/api/src/updates/update-checker.ts)

• Initial check still fires 10s after startup; the recurring tick now runs every hour instead of gating on a 24-hour window.
• Added foreground/online triggers (visibilitychange → visible, focus, online), throttled to 5 minutes based on the most recent attempt or successful check. Failed attempts also count toward the throttle, so a flapping network can't produce request storms; manual checks bypass it.
• Server switch triggers an immediate check and clears the previous server's verdict / ready version.
• All automatic triggers respect the "auto check" setting; manual checks keep working when it is off.
• initUpdateChecks() now returns a stop function that clears the timers, the sync-status subscription, the base-URL subscription, and all DOM/window listeners. Stopping also cancels checks waiting on a server switch.

Robustness across server switches

• /health is requested with an explicit baseURL snapshot and a 15s timeout.
• A generation counter plus a base-URL/shell identity check discards stale successes, failures, and download results from a previous server so they never publish an out-of-date prompt.
• Installer preparation is serialized on switch: the in-flight prepare is awaited before querying the new server, avoiding two native downloads racing over the same pending-install slot.

Installer reuse

• A version prepared by the current platform shell is reused for the rest of the run (preparedVersion); a version with no published package yet is retried on the next check. Registering a different shell resets the cache.

API client (packages/api/src/api/client.ts)

• New onApiBaseUrlChange(listener) subscription. setApiBaseUrl now notifies only on an actual value change.

Docs

• Updated spec.md and issue 03 to reflect the new cadence and triggers; added issue 07 documenting the delivered behavior and acceptance criteria.

Testing

update-checker.test.ts was extended from 12 to 211 lines of coverage, including the API-client subscription. All 55 update-check, verdict, and API-client tests pass, covering:

• hourly checks and startup delay,
• per-event throttling (focus, visibilitychange, online) and background events being ignored,
• throttle-on-failure with manual retry,
• disable/stop behavior and listener cleanup,
• server switch clearing state, discarding stale results, and serialized prepare,
• installer reuse and retry when a package is not yet published.

Real-device download and install acceptance remains tracked by issues 05 and 06.