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