Fix FAT Clock Sync control and immediate TRUE evidence

[masarray]

What changed

• Adds a real Clock Sync checkbox to the FAT workspace action row.
• Checkbox defaults ON to preserve v1.6.24 behavior.
• Unchecking stops the ARSAS SNTP service while leaving IEC 61850 monitoring untouched.
• Re-checking re-attaches the Clock Sync lifecycle to connected IEDs and resumes the SIPROTEC-compatible SNTP profile.
• Raises FAT evidence dispatcher priority from Background to DataBind so a TRUE edge is evaluated and its ON evidence is bound before the next UI render instead of being delayed until a later FALSE edge under busy live monitoring.

Audit finding

The transition evaluator already captures ON evidence on the FALSE→TRUE edge. The delay was downstream: the FAT session controller drain was scheduled through WPF at DispatcherPriority.Background, allowing live UI/monitor traffic to postpone evidence processing. The timestamp columns continue to display actual relay timestamps only; this patch does not substitute laptop time for missing relay t values.

Safety invariants

• Clock Sync OFF never disconnects IEC 61850.
• ARSAS still does not stop or reconfigure Windows Time.
• Existing UDP/123 fail-open behavior remains unchanged.
• SNTP remains SIPROTEC compatibility stratum 2; no GPS/PTP/stratum-1 claim.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Guard queued reconciles when Clock Sync is disabled

If IsConnected changes on a runtime thread just before these handlers are removed, ClockSyncDevice_PropertyChanged may already be enqueuing ScheduleClockSyncReconcile on the dispatcher. While this method awaits StopAsync, that queued reconcile can wait behind _clockSyncIntegrationGate and then restart the SNTP service after the stop completes, because neither scheduling nor EnsureClockSyncForDeviceAsync checks _clockSyncEnabled. In that race, the unchecked control continues serving and broadcasting time; recheck the enabled state after dispatching and after acquiring the gate, or cancel pending reconciles.

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