fix: stop synthesizing omitted sync conflicts

[TimRl]

fix: stop synthesizing omitted sync conflicts

Summary

Prevent Codex from turning diagnostic paths omitted from Frontier’s conflict list into fabricated conflicts. This previously caused remote files to be materialized, processed, and potentially committed as local work.

This PR works with the corresponding Frontier changes, which provide authoritative conflict information and the Git snapshot used during analysis.

Changes

• Use remoteChangedFilePaths as the authoritative conflict-list diagnostic.
• Stop using allChangedFilePaths, which also contains local-only changes.
• Retry safely when Frontier’s remote-change diagnostics disagree with its conflict list.
• Never synthesize missing conflicts or write guessed remote content into the working tree.
• Complete divergent histories even when Frontier resolved every change and Codex has zero file resolutions.
• Pass the analyzed local, remote, and merge-base commits back to Frontier during merge completion.
• Optimize stream-only post-sync cleanup by filtering existing pointer stubs before replacement.
• Preserve compatibility cleanup when upload information is empty or omitted.
• Continue processing media explicitly reported as uploaded.

Test Checklist

• Path normalization covers separators, prefixes, and Unicode.
• Missing conflict entries stop safely without synthesizing files.
• A large omitted remote set is never materialized.
• Empty and omitted LFS upload reports retain compatibility cleanup.
• Existing pointer stubs are excluded from expensive replacement.
• Explicitly uploaded media is still converted back to pointers.
• npm run compile
• npm run lint
• Extension test suite: 1,513 passing, 10 pending

[LeviXIII]

Syncing at same time works as well.