[BUG] Diff panels not cleared when new suggestion is shown — stale diffs accumulate until window focus change

## Bug Description

After the latest update, sometimes diff panels shown in Neovim are not cleared when Claude Code proposes a new change. Previous diffs remain visible in the split panels and accumulate over time. The only way to dismiss them is to manually switch focus to the LazyVim tab.

## To Reproduce

Steps to reproduce the behavior:

1. Open Ghostty with a tab split in two panes: Claude Code on one side, LazyVim on the other.
2. Start the Claude Code integration in Neovim.
3. Ask Claude to make a change to a file — a diff is shown in the split panels.
4. Ask Claude to make a second (different) change to the same or another file.
5. Observe that the previous diff is still visible alongside the new one — diffs accumulate.

## Expected Behavior

When Claude Code proposes a new change, any previously displayed diff panels should be cleared/replaced, so that only the current suggestion is visible.

## Environment

- Neovim version: 0.11.6
- Claude Code CLI version: 2.1.70
- OS: macOS 26.3
- Plugin version: commit 432121f

## Error Messages

No explicit error messages — visual/rendering issue only.

## Additional Context

The issue seems to be related to focus/window state: switching focus to the LazyVim pane forces the stale diffs to disappear. This suggests the diff buffers or windows are not being properly closed/reset when a new suggestion is triggered.

Start in the Neovim Claude Code integration path that handles a new suggestion and manages diff buffers or windows; the issue does not name specific files or tests. Reproduce with two successive changes, then verify that only the current diff remains visible and that switching focus is no longer needed to clear stale panels.

Written by the indexing model from the issue text.