feat(core): hash entity identifiers if too long for db engine

[AlessandroPomponio]

Summary

This PR adds automatic hashing for long entity identifiers to prevent database field length violations. The entity identifier is used as a primary key in SQLSampleStore. When an entity identifier exceeds 700 characters, it is now hashed using SHA256 to ensure it stays within the 768-character INNODB (MySQL) database limit for columns used as indexes while maintaining uniqueness and determinism.

NOTE: this issue stems from a limitation of the INNODB engine on MySQL when used with the utf8mb4 charset. Attempting to create a VARCHAR column with an index on it (such as a primary key) that is above 768 characters would fail with the following error:

SQL Error [1071] [42000]: Specified key was too long; max key length is 3072 bytes

3072/4 = 768 is the maximum length possible

Resolves #382

Files Changed

📄 orchestrator/schema/entity.py

Modified the entity_identifier_from_properties_and_values function to handle long identifiers. The function now checks if the generated identifier exceeds 700 characters (safe threshold below the 768-character database limit). If it does, the identifier is hashed using SHA256 and prefixed with "hash-" to indicate it's a hashed value. Short identifiers remain human-readable for debugging purposes.

📄 tests/schema/test_entity.py

Added comprehensive test coverage for the new identifier hashing functionality:

• test_entity_identifier_short_not_hashed: Verifies short identifiers remain unchanged and human-readable
• test_entity_identifier_long_hashed: Confirms long identifiers (4539+ chars) are properly hashed with the "hash-" prefix and stay within database limits (69 chars total)
• test_entity_identifier_different_points_different_identifiers: Ensures different input points produce unique identifiers for both short and long cases
• test_entity_identifier_threshold_boundary: Tests edge cases at exactly the 700-character threshold to verify the cutoff works correctly

[michael-johnston]

We should probably note in title and description the dB that has the restriction e.g MySQL has a x limit in primary keys. Since entity id is primary …

should also note if/if not SQLite has similar issue

[AlessandroPomponio]

@michael-johnston let me know if this is better
Feel free to make suggestions otherwise