Stable sort for school escorting

[americalexander]

Address multiple locations where the school escorting model does not sort in a stable manner. Also use 64-bit integers for tour and person IDs.

Changes

Stable Sorting

Added kind=""stable"" to sort_values calls throughout the school escorting model to ensure deterministic, reproducible results regardless of the initial row ordering of input data. Without stable sorting, ties in the sort key can be broken arbitrarily, leading to non-reproducible outputs across runs or platforms.

Affected locations:

• determine_escorting_participants: stable sort of chaperones by chaperone_weight (descending) when assigning chaperone_num, and stable sort of escortees by age (ascending) when assigning escortee_num
• school_escorting: stable sort of school escort tours by household_id and school_escort_direction before further processing
• create_pure_school_escort_tours: stable sort of pure escort tours by household_id, person_id, and start time

64-bit Integer Types

Replaced .astype(int) with .astype(""int64"") for tour IDs, person IDs, and related integer columns. Using the platform-native int type can produce 32-bit integers on Windows, which risks integer overflow for large ID values and inconsistent behavior across operating systems.

Affected locations:

• chauf_num and chauf_id in create_school_escorting_bundles_table
• Column values in join_attributes
• tour_id in create_chauf_escort_trips
• num_escortees in process_tours_after_escorting_model

[Copilot]

Pull request overview

This PR improves determinism and cross-platform consistency in the school escorting model by (1) enforcing stable sorting where ordering affects assignment/processing and (2) standardizing key ID/counter columns to 64-bit integers to avoid Windows 32-bit int pitfalls.

Changes:

• Add kind="stable" to key sort_values calls to make tie-breaking deterministic.
• Replace platform-native astype(int) casts with astype("int64") for tour/person-related integer columns.
• Apply stable ordering before downstream computations (e.g., pure escort tour construction and escort bundle ordering).

Reviewed changes

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

File	Description
activitysim/abm/models/util/school_escort_tours_trips.py	Uses int64 for ID-like columns and applies stable sorting when ordering impacts pure escort tour processing.
activitysim/abm/models/school_escorting.py	Applies stable sorts in participant numbering and bundle ordering; switches chauffeur-related numeric fields to int64.

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[jpn--]

@americalexander Is this PR motivated by an actual finding of non-reproducibility, or just having discovered the theoretical potential of such?

[janzill]

@jpn-- this is an actual problem, we found this independently when looking into unexpected differences in EET scenarios, let's discuss this in today's engineering meeting. I think it would be good to have a test here that shows how this manifests and how the new code fixes it.

[americalexander]

As Jan mentioned, this was something we discovered in practice. CCing @dhensle