Reject colliding PythonInterpreter file mounts

[isaacbmiller]

Summary

• reject distinct host files that would map to the same /sandbox/<basename>
• allow the same canonical file to be configured for both reading and writing

Why

PythonInterpreter flattens configured file paths to basenames. Two files such as first/config.json and second/config.json therefore become one guest file, and sync can write that guest value back to both host paths.

Rejecting the ambiguous configuration preserves the existing guest path convention without adding a new mapping API in a patch release.

Size

The implementation is 8 added production lines. The remaining diff is focused regression coverage.

Verification

• full Deno interpreter test file: 101 passed
• collision and canonical-dedup regressions: 2 passed
• CI-equivalent Ruff check and git diff --check passed

[greptile-apps]

Greptile Summary

The interpreter now rejects mount configurations that would expose different host files under the same sandbox filename, while preserving repeated references to the same canonical file.

Confidence Score: 5/5

No blocking failure remains.

The exercised alias and basename collision path is rejected during interpreter construction before sandbox mounting begins.

T-Rex Logs

What T-Rex did

• Ran the interpreter-alias collision test script to validate that alias collisions prevent sandbox mounting, and observed a pre-mount rejection with a mounting-basename error.
• Repeated the exact same collision test command and again saw a pre-mount rejection with the same error, confirming that the conflict cannot reach the sandbox mounting phase.

_{Ran code and verified through T-Rex}

_{Reviews (2): Last reviewed commit: "Handle aliased mount collisions" | Re-trigger Greptile}