fix: normalize Windows backslash paths in file watcher to fix tree refresh

[skyzhao1223]

Issue for this PR

Closes #38125

Type of change

• Bug fix

What does this PR do?

File tree and file viewer do not auto-refresh after AI edits on Windows because path.normalize() preserved backslashes while tree-store and watcher's split('/') expected forward slashes, causing path lookup mismatches and preventing directory refresh.

• path.ts — normalize() now converts backslashes to forward slashes on Windows, consistent with normalizeDir() and encodeFilePath() which already do this
• watcher.ts — adds defensive .replace() after normalization as a safety net
• session.tsx — normalize path separators in VCS watcher .git/ filter so Windows backslash paths don't bypass the guard
• path.test.ts — updated Windows path normalization test expectations

Note on PR #41240 (potential duplicate)

PR #41240 (core/filesystem/watcher.ts) and this PR fix the same root problem (Windows backslash vs forward slash mismatch) at different layers and are complementary:

• fix(core): normalize file watcher paths to forward slashes #41240 normalizes the watcher path at the event source in packages/core, so every file.watcher.updated consumer benefits.
• This PR fixes the app-layer consumers: path.normalize() now returns forward slashes on Windows (resolving an inconsistency with normalizeDir()/encodeFilePath()), plus a defensive replace in invalidateFromWatcher() and the session.tsx VCS .git/ filter.

Both are small and apply to separate packages/files; merging one does not conflict with the other. Happy to rebase/trim if maintainers prefer a single approach.

How did you verify your code works?

• Tested the normalize and watcher invalidate logic in isolation with Bun
• Existing test suite expectations updated to match new behavior

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Found a potential duplicate:

PR #41240: fix(core): normalize file watcher paths to forward slashes
#41240

This PR appears to address the same issue as the current PR #41931 — normalizing file watcher paths on Windows by converting backslashes to forward slashes. Both PRs target path normalization in the file watcher to fix tree refresh behavior.

You should check if PR #41240 is already merged or if it's still open, as it may duplicate the work being done in PR #41931.

[github-actions]

Automated PR Cleanup

Thank you for contributing to opencode.

Due to the high volume of PRs from users and AI agents, we periodically close older PRs using automated criteria so maintainers can focus review time on the most active and community-supported contributions.

This PR was closed because it matched the following cleanup criteria:

• The PR was created more than 1 month ago
• The PR had fewer than 2 positive reactions
• Positive reactions are counted as thumbs-up, heart, celebration, or rocket reactions on the PR

PRs created within the last month are not affected by this cleanup.

If you believe this PR was closed incorrectly, or if you are still actively working on it, please leave a comment explaining why it should be reopened. A maintainer can review and reopen it if appropriate.

Thanks again for taking the time to contribute.