[kitlangton]

Clicking a background shell in the pill now shows that shell's live output, with Stop, right in the menu.

Before: clicking a shell row in the pill closed the menu and scrolled the chat to the shell call, which shows no output. To see what a dev server or test watcher was printing, you had to ask the agent.

After: clicking a shell row turns the menu into a wider panel for that one shell: a back arrow, the command, how long it has run, Stop, and the last 14 lines of its output, live. Stop or an exit swaps Stop for how the shell ended ("Stopped", "Exited with code 1") instead of the panel vanishing. Escape closes it; the back arrow returns to the list and to the row you came from. This is option 3 of D-38 on the board.

Clip (open, back, open the watcher, Stop): https://problems.kitlangton.com/media/PaPQzmQK2hQaMzPJWCuYlw.mp4

  shell row onSelect
-   close menu, scroll the timeline to the shell call
+   keep menu open, panel.open(shell)
+     header: ← · command · elapsed · Stop | "Exited with code N" / "Stopped"
+     body:   followShellOutput(shell) → stripAnsi → last 14 lines, wrapped, no horizontal scroll
  shell leaves the running list while shown
+   ask shell.get how it ended; keep the panel, frozen elapsed, until back or close

Output	the timeline's own followShellOutput and stripAnsi, so it reads the same as an expanded shell call
Motion	none for list ↔ panel; the menu keeps its existing open fade
Stacked on	#59480; merge that first

Visual

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    .line{animation:line 4s linear infinite}
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    @keyframes panel{0%{opacity:0}35%,100%{opacity:1}}
    @keyframes line{0%,40%{transform:translateY(0)}100%{transform:translateY(-12px)}}
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  </g>
  <g class="panel">
    <rect x="20" y="4" width="200" height="50" rx="6" stroke="currentColor" stroke-opacity=".3"/>
    <path d="M32 12h-6m0 0 3-3m-3 3 3 3" stroke="currentColor" stroke-opacity=".7" stroke-width="1.2"/>
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</svg>

Read: activity-chips.tsx (the panel and focus) and shell-panel.ts (its state). Checks: app typecheck, the 6 shell-panel unit tests and both activity-chips component tests pass. The existing elapsed-time component test needed the story's items to keep their start time (they were rebuilt with a fresh Date.now() on every read) and a paused clock. Argon review not run: no subagent tool in this session. Beta's e2e legs are known red until #59427.