Remove browser CustomEvent publishing from ObservableQueryDiagnostics

[Copilot]

Summary

ObservableQueryDiagnostics was publishing a browser CustomEvent on every snapshot, which crashes on React Native/Hermes where CustomEvent is not available. This change removes that browser event path and keeps diagnostics transport purely API-based.

private _publishSnapshot(snapshot: ObservableQueryDiagnosticsSnapshot): void {
    this._snapshots.next(snapshot);
}

Added

• Added a diagnostics spec that asserts snapshot publishing does not dispatch browser events (ObservableQueryDiagnostics crashes on React Native / Hermes due to missing CustomEvent #2260)

Changed

• Changed ObservableQueryDiagnostics._publishSnapshot() to emit snapshots only via snapshots$ (ObservableQueryDiagnostics crashes on React Native / Hermes due to missing CustomEvent #2260)
• Updated diagnostics docs to state updates are exposed through getSnapshot() and snapshots$, not window events (ObservableQueryDiagnostics crashes on React Native / Hermes due to missing CustomEvent #2260)

Fixed

• Fixed React Native/Hermes crash caused by new CustomEvent(...) during diagnostics publication (ObservableQueryDiagnostics crashes on React Native / Hermes due to missing CustomEvent #2260)

Removed

• Removed window.dispatchEvent(new CustomEvent('cratis:observable-query-diagnostics', ...)) from diagnostics publishing (ObservableQueryDiagnostics crashes on React Native / Hermes due to missing CustomEvent #2260)

Security

• None (ObservableQueryDiagnostics crashes on React Native / Hermes due to missing CustomEvent #2260)

Deprecated

• None (ObservableQueryDiagnostics crashes on React Native / Hermes due to missing CustomEvent #2260)

[github-actions]

NuGet packages for this PR, e.g. Cratis.Arc:
https://github.com/cratis/arc/packages/1655206?version=20.30.0