fix: normalize maintainer input paths

[nightcityblade]

Summary

Normalize Windows separators before matching paths against MAINTAINERS entries.

Motivation

Fixes #596.

Target and compatibility impact

Windows-style and repository-style paths now select the same maintainers.

Validation

• python3 -m unittest tools.test_get_maintainer (1 passed)
• python3 -m ruff check tools/get_maintainer.py tools/test_get_maintainer.py
• git diff --check

Checklist

• Commits include a DCO Signed-off-by line.
• Tests cover new behavior or the PR explains why no test is needed.
• User-facing changes include documentation or diagnostics updates.
• The change preserves the license boundary between the compiler and std/.

[LunaStev]

There is a conflict with #604 because both PRs add tools/test_get_maintainer.py with different contents.

Please rebase this PR onto the latest master after #604 is merged and resolve the conflict by keeping the tests from both changes in tools/test_get_maintainer.py.

The implementation itself looks good; this is just to avoid losing either test set during the merge.

[nightcityblade]

Rebased onto the latest master after #604 and resolved the test conflict by keeping both test cases in tools/test_get_maintainer.py. Validation: python3 -m unittest tools.test_get_maintainer passed and git diff --check passed. The two Windows ARM64 failures on the previous run were target runtime crashes/timeouts unrelated to this Python-only change; the rebase will trigger a fresh CI run.

[LunaStev]

Rebased onto the latest master after #604 and resolved the test conflict by keeping both test cases in tools/test_get_maintainer.py. Validation: python3 -m unittest tools.test_get_maintainer passed and git diff --check passed. The two Windows ARM64 failures on the previous run were target runtime crashes/timeouts unrelated to this Python-only change; the rebase will trigger a fresh CI run.

LGTM. Thanks for resolving the conflict with #604 and preserving both test cases.

The path normalization and regression coverage now match #596 cleanly. The remaining macOS ARM64 CI failure is unrelated to this change.