fix(opencode): normalize subdirectory git paths

[mrbob-git]

Issue for this PR

Closes #25593

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

When opencode is opened from a subdirectory, Git can report paths relative to the repo root. The review UI then tries to read those paths relative to the opened directory and fails.

This normalizes Git status/diff/stat paths to the active directory, reads git show targets relative to the active directory, and keeps batched patch keys aligned with the normalized file paths.

How did you verify your code works?

From packages/opencode:

• bun test --timeout 30000 test/git/git.test.ts -t "show\(\) reads files relative to a subdirectory|status\(\) handles special filenames|diff\(\), stats\(\), and mergeBase|patch\(\) returns capped|show\(\) returns empty text for binary blobs"
• bun test --timeout 30000 test/project/vcs.test.ts -t "diff\('git'\) returns paths relative to the active subdirectory|diff\('git'\) returns uncommitted changes|diff\('git'\) keeps batched patches aligned"
• bun test --timeout 30000 test/file/index.test.ts -t "detects modified file|detects modified files relative to a subdirectory|detects untracked file as added|detects deleted file|detects mixed changes|returns empty for non-git project|returns diff and patch for modified tracked file"

Screenshots / recordings

Not a UI change.

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:

Based on my search, I found one potentially related PR (excluding the current PR #25631):

Related PR:

• PR feat(session): add support for per-session working directories #9365: feat(session): add support for per-session working directories
  • This may be related as it deals with working directory handling, though it appears to be a broader feature rather than a bug fix for git path normalization

However, this is an older feature PR from a different context. The current PR #25631 appears to be the only active PR directly addressing the git path normalization issue for subdirectories (issue #25593).

No duplicate PRs found

[github-actions]

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