Diff preview windows are unlabeled and appear in random panels — unusable with multiple sessions

Bug Report — High Priority

Problem

When Claude Code edits a file, the diff preview window opens in a random VS Code editor group with no indication of which Claude session triggered it. With multiple Claude sessions open (a supported workflow), this creates total chaos:

1. No session label — the diff window doesn't say which Claude requested the edit
2. Random placement — the diff opens in whatever editor group VS Code picks, often next to an unrelated Claude session
3. Blue approve buttons everywhere — multiple edits from different sessions stack up, impossible to tell which belongs to which session
4. Cannot be disabled independently — there is no setting to suppress the diff preview while keeping the approve/reject prompt in the Claude panel itself

Expected Behavior

• Diff previews should open adjacent to the Claude panel that requested the edit, not in a random editor group
• Each diff preview should be labeled with the session name/ID
• There should be a setting to disable diff preview popups while still requiring approval via the Claude panel's inline prompt

Environment

• Claude Code v2.1.39 (VS Code extension, macOS)
• 4 Claude sessions open simultaneously

Related

• #25299 (split panel button duplicates sessions)
• #25295 (sessions split/swap between panels)