Fix missing source locations in Python → Laurel translation

[keyboardDrummer-bot]

Summary

Fixes #842 — Adds missing source location metadata in PythonToLaurel.lean so that diagnostics in the expected_laurel tests no longer report "unknown location".

Root Cause

Three places in PythonToLaurel.lean were producing nodes with defaultMetadata (which has FileRange.unknown) instead of passing through the source location from the Python AST:

1. Return type constraint ensures — pyFuncDefToPythonFunctionDecl used returns.ann (the Ann wrapper's annotation, which is {0,0} for DDM-generated optional fields) instead of retTy.ann (the actual return type expression's source range).

2. For-loop assume statements — The PIn, Any_to_bool, and range-check Assume nodes in the For case of translateStmt used mkStmtExprMd (unknown location) instead of mkStmtExprMdWithLoc with the for-statement's md.

3. Return statement — The LaurelResult assignment and Exit "$body" in the Return case used mkStmtExprMd instead of mkStmtExprMdWithLoc with the return-statement's md.

Changes

• Strata/Languages/Python/PythonToLaurel.lean — 3 targeted fixes (described above)
• StrataTest/Languages/Python/expected_laurel/*.expected — 15 test expectation files updated (all unknown location: prefixes replaced with actual file(line, col): locations)

Verification

• lake build succeeds
• run_py_analyze.sh passes all tests
• grep "^unknown location:" expected_laurel/*.expected returns zero matches

[keyboardDrummer-bot]

The CI failure was caused by the branch being behind main. Specifically, PR #823 ("Add synthetic Python tests covering many Python constructs") merged into main after this branch was created, adding new test expected files — test_for_else_break.expected and test_list_empty.expected — that contained unknown location strings (since they were generated without our source location fix).

Fix: Merged main into this branch and regenerated the two affected expected files so they now contain the correct source locations instead of unknown location.

Verified locally:

• lake build succeeds
• run_py_analyze.sh passes all tests (including the two newly updated ones)
• grep "unknown location" expected_laurel/*.expected returns zero matches

[MikaelMayer]

Thank you very much !!