Session rollover

[CodingInAVan]

Description

Account serialized bytes across rollover segment loggers

Run-part byte rollover now accounts for every accepted NDJSON write across all segment loggers, not only the initial logger.

• Add a serialized-byte callback after successful file-sink writes.
• Bind the initial logger to Part 1 before its first write.
• Rebind every replacement logger to its current RunPartContext before bootstrap events.
• Forward per-part byte deltas to SegmentCoordinator.
• Cover accepted/rejected writes, fan-out, callback binding, saturation, ordinary cuts, and multi-part byte rollover.

Type of Change

• Bug fix
• New feature
• Documentation update

Testing

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas