Fix blank git diff view on Windows when working in a subfolder

[HiteshRohira]

Context

Fixes a Windows path handling bug in crates/util/src/paths.rs when computing a relative path via strip_prefix. (Closes #51758 )

Previously, Windows prefix matching only handled drive-letter case-insensitivity. It could still fail when the parent and child paths referred to the same location but used different separator styles (\ vs /) or different casing in later path segments. That caused valid Windows paths to return None instead of a relative path, which caused the diff to break.

This change normalizes Windows paths for prefix comparison by lowercasing any ASCII characters and converting backslashes to forward slashes before checking the prefix.

Tests were added for mixed-case and mixed-separator Windows paths to cover the bug and prevent further regressions.

How to Review

1. Check the strip_prefix Windows branch to confirm the new normalization logic only affects prefix comparison and still rejects partial-segment matches.
2. Check the added tests for mixed separator and mixed casing cases on Windows paths.

Self-Review Checklist

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Release Notes:

• Fix blank git diff view on Windows when working in a subfolder

[cole-miller]

Thanks @HiteshRohira!

This change makes sense in the abstract, but I'd like to understand how it fixes the issue you're seeing. Are you seeing that we're not successfully doing abs_path_to_repo_path on Windows in the case of a repository root above the worktree root? If so, what do the paths involved look like? I'm curious because it seems like in that codepath the repository root is ultimately constructed from one of the Path::ancestors of the worktree root, so I'm not sure how they end up with different casing or separators.

Also cc @reflectronic who is more knowledgeable about Windows paths than I am.

[HiteshRohira]

This is what the differences in paths were looking like. This comes from logs in the strip_prefix function

child="C:\\Users\\hites\\code\\Test\\Test2/Testaa3/Test4/Testing5/Test6/whytho.md" parent="C:\\Users\\hites\\code\\Test\\Test2\\Testaa3\\Test4"
child="C:\\Users\\hites\\code\\Test\\Test2/Testaa3/Test4/Testing5/test2.md" parent="C:\\Users\\hites\\code\\Test\\Test2\\Testaa3\\Test4"
child="C:\\Users\\hites\\code\\Test\\Test2/Testaa3/Test4/test.md" parent="C:\\Users\\hites\\code\\Test\\Test2\\Testaa3\\Test4"

@cole-miller thank you for the pushback on this, the bug ended up being in a different place. When zed was joining paths in repo_path_to_abs_path it produced mixed paths like

C:\Users\hites\code\Test\Test2/Testaa3/Test4/test.md

When that path went into find_worktree and from there into strip_prefix it failed because it was receiving something like this

child  = C:\Users\hites\code\Test\Test2/Testaa3/Test4/test.md
parent = C:\Users\hites\code\Test\Test2\Testaa3\Test4

I have fixed repo_path_to_abs_path such that it first converts the repo path

[devoper2022]

can we know the status of this PR

[HiteshRohira]

@devoper2022 just waiting for approval

[devoper2022]

@Anthony-Eid can you review this PR

[reflectronic]

Thank you