[BUG] Desktop app: scroll wheel captured by Edit/Write diff cards even when diff has no overflow

What's Wrong?

In the Claude Code desktop app, Edit/Write diff cards capture scroll wheel and trackpad input whenever the cursor is over them — even when the diff is only one or two lines and has nothing to scroll. The outer conversation does not advance until you move the cursor off the diff card.

For diffs large enough to have internal overflow, the same problem manifests as a scroll trap: the inner diff scrolls to its boundary, then further scroll input is dropped instead of chaining to the outer chat.

This happens both for:

• Pending Edit/Write approval prompts (the diff card shown before you accept the edit)
• Completed Edit/Write tool results (the diff card in transcript history after the edit applied)

What Should Happen?

• A diff card with no overflow should not intercept scroll input at all — it should pass straight through to the outer conversation.
• A diff card with overflow should scroll-chain: once the inner scroll hits its top/bottom boundary, additional input should bubble up to the outer chat (overscroll-behavior: auto semantics).

Reading through a conversation that contains diff cards should not require repeatedly repositioning the cursor onto non-diff regions.

Steps to Reproduce

1. Open any conversation in the desktop app that contains one or more Edit/Write tool results (a one-line diff is sufficient).
2. Place the cursor over a diff card.
3. Scroll down with the wheel or trackpad.
4. Observe: the outer conversation does not scroll. Move the cursor off the diff and scroll again — the conversation advances normally.

Environment

• Claude Code version: 2.1.145
• OS: macOS 15.6.1 (Darwin 24.6.0)
• Surface: Claude Code desktop app

Additional Information

Related but distinct issues found while searching:

• #60885 — Permission preview flickers / scroll snaps back on long Write/Edit content
• #60424 — /diff view can't be scrolled with keyboard
• #58660 — Scroll wheel doesn't scroll agent transcript inside agent detail view (same nested-scroll family)