feat: optimize aliased BatchCheck requests

[Siddhant-K-code]

Description

Adds an opt-in optimize_relation_aliases option to async and sync BatchCheck.

When enabled, the SDK:

• reads and caches the pinned authorization model;
• resolves only pure same-object computed-userset aliases;
• combines checks only when user, object, context, and contextual tuples are identical;
• maps the server result back to every original correlation ID and request.

The default BatchCheck behavior is unchanged.

Why

Applications often use intent-specific permissions that are pure aliases of a shared relation. Sending each alias as a separate item preserves a useful application-level contract, but can repeat the same authorization evaluation within one batch. This opt-in path keeps the original relations and correlation IDs visible to callers while reducing redundant checks.

Safety

• Requires an explicit authorization model ID.
• Caches aliases by store and immutable model ID.
• Does not optimize unions, intersections, differences, tuple-to-userset rewrites, other-object computed usersets, missing targets, or cycles.
• Preserves group boundaries across users, object types, object IDs, context, and contextual tuples.
• Preserves per-item allowed and error responses.

Testing

• 627 non-integration tests pass.
• Async and sync tests verify one canonical item per distinct group and map every result to its original correlation ID and request.
• Project coverage is 86%, above the unchanged 80% target.
• Changed executable lines have 100% diff coverage.
• Ruff formatting and linting pass.
• Mypy passes for the changed source files.

The README is generated; its source template should receive the equivalent update before merge.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.93%. Comparing base (62fbd9a) to head (ca6c3a4).

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #311       +/-   ##
===========================================
+ Coverage   69.93%   85.93%   +15.99%     
===========================================
  Files         142      143        +1     
  Lines       10774    10925      +151     
===========================================
+ Hits         7535     9388     +1853     
+ Misses       3239     1537     -1702     

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