codeSplitters code view: review an agent's batch before it lands (ghost diff, accept / hold / reject) #467

Follow-up to the claims PR. Today an agent's edit lands in one batch when the run ends. Instead, show it as a ghost diff over the lines (orange/grey diff colours) with Accept / Hold / Reject per chunk, auto-accepting after a few seconds unless someone is looking at or editing those lines. The same stack covers catching up after being away: step through what landed instead of the file changing silently. Edits where a person's version won get a small "kept yours" mark that shows what the agent wanted. Animations: changed lines cross-fade, deleted rows collapse (~200ms), new rows expand; the scroll anchor from the claims PR keeps the view still.