tui: background work hint is not clickable #57472

Description

In the v2 TUI, after a shell command or foreground subagent runs for about 3 seconds, the transcript shows Press ctrl+b to move running work to the background. The hint is plain text and ignores mouse clicks.

The Desktop/Web timeline renders the same hint as a clickable "Move to background" button, so the TUI looks broken for anyone reaching for the mouse. The ctrl+b keyboard path still works.

Source: BackgroundToolHint in packages/tui/src/routes/session/index.tsx renders a <text> with no onMouseUp; the app equivalent BackgroundMoveHint in packages/app/src/session/timeline/message-timeline.tsx is a <Button onClick>. Mouse capture is on and other TUI elements (composer list rows, esc) respond to clicks, so this is specific to the hint.

Related but distinct: #51903 (composer tab/footer hints) and #49216 (the ctrl+b keypress itself).

Plugins

none

OpenCode version

v2.1.1 (also present on dev 772e2ae)

Steps to reproduce

1. In the v2 TUI, ask the agent to run a shell command (or spawn a foreground subagent) that runs for more than 3 seconds.
2. Wait for the transcript hint Press ctrl+b to move running work to the background.
3. Click the hint.
4. Nothing happens; the work keeps running in the foreground.

Expected: clicking the hint runs session.background, the same action as ctrl+b and the Desktop button.

Screenshot

No response

Operating System

Pop!_OS 24.04 (Linux 7.2.6-76070206-generic, x86_64)

Terminal

Ghostty (TERM=xterm-256color, TERM_PROGRAM=ghostty, COLORTERM=truecolor), shell /bin/bash