Function deriveStatus

deriveStatus(
    declared: boolean,
    state: LayerPullState | undefined,
    maxAgeMs: number | undefined,
    now: number,
): LayerOfflineStatus
Decides ONE layer's status from its declaration and its marker.

The test order is the reading order, and it is not commutative: notDeclared trumps everything (an undeclared layer has no offline state to report), then the absent marker, then the failure, then the unfinished run, and staleness only comes last — on a pull that succeeded AND finished.
Parameters
- declared: boolean
  True when the layer declares a pull source (offline.source.url).
- state: LayerPullState | undefined
  The persisted marker, or undefined when no pull ever happened.
- maxAgeMs: number | undefined
  Expiry declared by the layer, or undefined.
- now: number
  Reference instant, injected to stay testable at a frozen clock.
Returns LayerOfflineStatus
The status, never guessed.
- Defined in packages/core/src/capabilities/offline/report/sync-report.ts:68