add trip scheduling choice explicit chunking

[jpn--]

Replaces and advances #1041.

This pull request adds support for explicit chunk sizing in the trip_scheduling_choice model, allowing users to control how data is split during processing. It also introduces comprehensive tests to ensure that explicit chunking works correctly and does not affect model results.

Explicit chunking support:

• Added an explicit_chunk parameter to TripSchedulingChoiceSettings, enabling users to specify a fixed chunk size or a fraction of the dataset for chunking.
• Updated run_trip_scheduling_choice to pass the explicit_chunk setting to chunk.adaptive_chunked_choosers, ensuring the chunking behavior follows user configuration.

Testing enhancements:

• Refactored the test for run_trip_scheduling_choice to use deep copies and proper random-number management, ensuring reproducibility when chunking is enabled. [1] [2]
• Added a test to verify that explicit chunking divides the data as expected and that results are identical to the default adaptive chunking.

[Copilot]

Pull request overview

Adds explicit chunk sizing to trip scheduling while preserving deterministic results.

Changes:

• Adds the explicit_chunk model setting and forwards it to the chunker.
• Adds coverage for chunk sizes and result equivalence.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
activitysim/abm/models/trip_scheduling_choice.py	Implements explicit chunk configuration.
activitysim/abm/test/test_misc/test_trip_scheduling_choice.py	Tests deterministic explicit chunking.

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[m-richards]

Thanks @jpn-- for following up on this!