Handle git rebase conflict output

[shanev]

Fixes #5560.

Summary

• Extended parse_git_apply_output so we capture conflicted paths from git rebase/git merge output (e.g. CONFLICT (content): Merge conflict in …, modify/delete conflicts).
• Added regression tests covering both the rebase transcript and a modify/delete scenario.
• Kept a conservative fallback: we now only return a path when we can positively identify it.

[shanev]

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