Preserve FIFO order when pausing HelperCustomQueue

[Niketion]

Summary

• Check the pause state before reading the next item from HelperCustomQueue<T>.
• Remove the mid-batch path that re-enqueued an already-dequeued item.
• Add focused regression tests for pausing during a batch and before enqueueing.

Root cause

The consumer previously dequeued an item before checking whether a pause had been requested. When paused, it wrote that item back to the same channel.

Re-enqueueing moved the item behind entries already in the channel, so an ordered sequence such as A, B, C could be processed as A, C, B.

This is particularly problematic for ordered market-data streams and exchange sequence handling.

Behavior

The consumer now checks the pause state before claiming the next item. An item already claimed because of a concurrent pause is processed once, and the following loop iteration observes the pause.

No shutdown, disposal, public API, monitoring, or connector behavior is changed.

Tests

• PauseDuringBatch_PreservesFifoOrder
• PauseBeforeEnqueue_DoesNotProcessUntilResume

Validation completed:

• Commons tests: 2 passed
• MarketResilience tests: 53 passed
• MarketData connector tests: 18 passed
• VisualHFT.Commons build: passed

[chatgpt-codex-connector]

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