fix: Fix data and target availability for daemon mode

[keelerm84]

Note

Adjust FDv1/FDv2 availability logic to properly report Cached/Defaults in daemon/disabled modes, and add/update tests to cover these scenarios.

• Datasystem
  • FDv1:
    • Track daemonMode (ExternalUpdatesOnly) and update DataAvailability() to avoid Refreshed in daemon mode; prefer Cached if store initialized, else Defaults.
    • Update TargetAvailability() to return Defaults when offline, Cached in daemon mode, else Refreshed.
  • FDv2:
    • Add daemonMode (no data sources, store present); set during init.
    • Update DataAvailability() to return Refreshed when selector defined; Cached when store initialized; otherwise Defaults.
    • Update TargetAvailability() to return Defaults when disabled, Refreshed when data sources configured, Cached in daemon mode, else Defaults.
• Tests
  • Add comprehensive FDv1/FDv2 availability tests across offline/daemon/normal modes and store states in internal/datasystem/data_availability_test.go.
  • Update client tests to initialize in-memory store for ExternalUpdatesOnly and verify behavior (ldclient_events_test.go, ldclient_external_updates_only_test.go).

^{Written by Cursor Bugbot for commit 1784d36. This will update automatically on new commits. Configure here.}