[BUG] restore destroys user changes if done in a chain #20781

Description

When users restored earlier messages while later messages in the same chain remained reverted, file changes from the restored messages could still stay missing on disk. This happened because the server updated the revert point without first restoring the saved pre-revert snapshot, so the repo state could fall out of sync with the revert stack

Plugins

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OpenCode version

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Steps to reproduce

1. Start a session in a repo with three files, for example a.txt, b.txt, and c.txt.
2. Create three messages where each message changes a different file:
   • message a changes a.txt
   • message b changes b.txt
   • message c changes c.txt
3. Revert from message a, so all three messages are reverted.
4. Restore message a, then restore message b, while leaving message c reverted.
5. Check the files on disk with cat

Expected

• a.txt and b.txt should be restored
• c.txt should still be reverted

Actual

• file changes from the restored messages could still remain missing on disk
• the repo state could be out of sync with what the UI showed as restored vs. still reverted

Screenshot and/or share link

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Operating System

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Terminal

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