Report error state when out of sync

[kahrendt]

Report error state when out of sync and report synchronized when recovered. Logs out of sync/resync events. This is required by the spec (https://github.com/Sendspin/spec/blob/133383e588bbf1ddcfcf9952626ede0bcdef79a3/README.md?plain=1#L175)

Closes #63

[Copilot]

Pull request overview

Implements protocol-required client state transitions for sync loss/recovery in the sync task, adding explicit ERROR reporting when playback falls out of sync and SYNCHRONIZED when alignment is regained, with logging around these transitions.

Changes:

• Add SyncContext flags to track alignment phases and edge-trigger ERROR/SYNCHRONIZED transitions.
• Emit client/state=ERROR once when sync is lost (outside alignment phases), and client/state=SYNCHRONIZED when in-tolerance sync is regained.
• Mark post-seek periods as “aligning” to avoid reporting expected hard-sync behavior as an error.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/sync_task.h	Adds aligning / reported_error flags to track alignment lifecycle and state transition edges.
src/sync_task.cpp	Reports ERROR on out-of-sync, reports SYNCHRONIZED on recovery, and treats post-seek as an expected alignment phase.

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