fix(program): disambiguate repeated Python symbols

[forhappy]

Summary

• disambiguate repeated Python function symbol IDs by occurrence
• preserve the existing stable ID for the first definition and derive deterministic IDs for later collisions
• add a Django-shaped regression test for conditional mogrify() definitions

Root cause

The Python Program IR extractor hashed source path, qualified name, and signature. Conditional implementations with the same name and signature in one file therefore emitted duplicate IDs and failed provider validation. Rust and TypeScript already applied occurrence-based disambiguation; Python did not.

Impact

Large Python repositories with conditional alternative definitions, including Django's psycopg 2/3 mogrify() implementations, can now complete compass init and compass update successfully.

Validation

• cargo fmt --all -- --check
• cargo test -p compass-languages (40 tests passed)
• Django full initialization: 6,051 files indexed, 3,038 Program IR modules, 0 conflicts
• Django cached update completed successfully