Fix sync issue

[TimRl]

fix: recover interrupted syncs without recommitting remote files

Summary

Prevent files left by an interrupted merge from being mistaken for new local work. Frontier now verifies remote-equivalent files against Git commits, the index, file mode, and actual disk bytes before excluding them from local commits.

The corresponding Codex PR consumes Frontier’s authoritative conflict list and carries the analyzed Git snapshot through merge completion.

Changes

• Fetch remote history before classifying working-tree files as local changes.
• Detect files that are byte-, mode-, index-, and commit-identical to the fetched remote.
• Exclude verified remote-equivalent files from LFS uploads and local commits.
• Adopt exact remote blobs into the index so interrupted syncs can fast-forward normally.
• Preserve missing files, local edits, staged differences, binary content, and executable-mode changes.
• Filter fully identical committed files from conflict analysis.
• Return the analyzed local, remote, and merge-base commits with conflict results.
• Reject merge completion when local or remote history changes after analysis.
• Complete verified divergent histories without creating stale merge commits.
• Stage valid LFS pointers directly without downloading or hydrating their media.
• Support index inspection and updates through both native Git and the built-in Git adapter.
• Resolve both Electron and Code executable names in cached macOS VS Code installations.

Test Checklist

• Verify identical-file detection through native and built-in Git adapters.
• Preserve missing, modified, staged, binary, and mode-different files.
• Recover 1,500 interrupted remote additions without a local recovery commit.
• Fast-forward 1,500 verified remote-equivalent files.
• Converge histories containing a prior identical-pointer commit.
• Reject merge completion when the remote advances after analysis.
• Stage LFS pointers without hydrating media.
• Validate current and legacy macOS VS Code executable names.
• Run the VS Code test suite and package successfully with cached VS Code 1.135.0.