Add hybrid CASE_HASH support

[tomvothecoder]

Summary

• parse and persist CASE_HASH from env_case.xml
• keep case-name-based grouping as the authoritative resolver
• warn when CASE_HASH drifts across executions for the same case name
• expose case_hash on simulation schemas and add a migration for simulations.case_hash
• closes [Enhancement]: Evaluate CASE_HASH as the canonical Case identifier #136

Why not group by CASE_HASH yet?

Issue #136 now has confirmed real-world evidence that CASE_HASH can be consistent across some executions and drift across others for the same logical case. Making it the sole grouping key now would risk splitting one logical case into multiple SimBoard cases.

This change implements the safe hybrid path:

• store CASE_HASH
• make it available for diagnostics and future evaluation
• retain existing case-name grouping when hashes conflict or are missing

Testing

• uv run pytest tests/features/ingestion/parsers/test_case_docs.py tests/features/ingestion/test_ingest.py tests/features/simulation/test_schemas.py tests/features/simulation/test_api.py
• make backend-test

Refs #136

[Copilot]

Pull request overview

Adds hybrid support for CASE_HASH by parsing it from env_case.xml, persisting
it on simulations, and exposing it via simulation schemas/API while keeping
case-name-based grouping authoritative and emitting warnings on hash drift.

Changes:

• Parse CASE_HASH into ingestion metadata and persist it on Simulation.
• Add simulations.case_hash via Alembic migration and expose caseHash in
  SimulationCreate/SimulationOut.
• Add drift-detection logic that warns on conflicting hashes for the same case
  name (without changing grouping), plus test updates.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
backend/app/features/ingestion/ingest.py	Tracks CASE_HASH observations during ingestion and logs drift warnings.
backend/app/features/ingestion/parsers/case_docs.py	Parses CASE_HASH from env_case.xml into metadata.
backend/app/features/ingestion/parsers/parser.py	Plumbs parsed case_hash into ParsedSimulation.
backend/app/features/ingestion/parsers/types.py	Extends ParsedSimulation with optional case_hash.
backend/app/features/simulation/models.py	Adds nullable case_hash column to ORM model.
backend/app/features/simulation/schemas.py	Exposes case_hash on create/out schemas with descriptions.
backend/migrations/versions/20260414_000000_add_case_hash_to_simulations.py	Adds case_hash column to simulations table.
backend/tests/features/ingestion/parsers/test_case_docs.py	Verifies CASE_HASH is parsed (or None on read error).
backend/tests/features/ingestion/test_ingest.py	Verifies persistence of case_hash and drift warning behavior.
backend/tests/features/simulation/test_api.py	Asserts caseHash is returned by simulation GET endpoint.
backend/tests/features/simulation/test_schemas.py	Updates schema tests to include caseHash/case_hash.

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