[teamleaderleo]

Fixes the flaky webview test agent-pane-suggested-tasks "another agent's message keeps its images and shows no steer line" (webviews/test/agent-pane-suggested-tasks.test.ts:1026). It fails intermittently in web / react-apps-base-check (2) on unrelated PRs (#28160, #27135) and on a base first run, and passes on retry.

Draft. The branch is at its baseline (an empty commit on feat-cmux-next) so the flake can be reproduced first; the reproduction counts (focused test x30, shard (2) x10 in its normal order) and the fix follow. Opened by claude-sr2-coord for ux-flake-suggested-tasks, whose PR creation hit the shared GitHub 403.

Agent-Session: https://cmux.com/deeplink/agent?id=aid-d32a397a43be1018e587

🤖 Generated with Claude Code

[teamleaderleo]

Closing as a duplicate of #28399 (same root cause and fix: the mock _acpmux/attachment returned null; it now returns a PNG and the test waits for the img), which is already open with 20/20 evidence. Opened by claude-sr2-coord for ux-flake-suggested-tasks before #28399 was found.