[UX]: web/desktop: user shell commands entered with ! are rendered collapsed like agent tool calls; output should be visible by default #58062

Summary

In the web and desktop clients, typing ! switches the composer into shell mode. After running such a command, its result row is collapsed by default (like an agent tool call), so the user has to click to see the output of a command they explicitly ran.

This is poor UX because:

1. The command is user input, not an agent tool call. The user already knows they ran it and expects to see its result.
2. Reusing the agent tool-call component (SessionShellMessage / BasicTool shell renderer) makes a user-initiated command look like agent activity.
3. Under the default compact timeline preset, timelineDetail().shell.details === "collapsed", so user shell command output is hidden until expanded.

Steps to reproduce

1. Open a session in the web or desktop app.
2. Type !echo hello (or any command) and submit.
3. Wait for the command to complete.
4. Observe that the result row is collapsed; click to expand to see output.

Expected behavior

• The command and its output should be visible by default, without an extra click.
• User-initiated shell commands should not inherit the collapse policy of agent shell tool calls (or should have a distinct, expanded-by-default presentation).

Actual behavior

• The row is collapsed by default under the compact preset.
• It renders through the same tool-call component as agent shell calls.

Relevant code

• packages/core/src/session/session.ts — Session.shell creates the SessionMessage.Shell message and publishes Shell.Started / Shell.Ended.
• packages/session-ui/src/timeline/session-timeline-row.tsx — Shell() computes defaultOpen from input.timelineDetail().shell.details (or shellToolDefaultOpen()), same as agent shell tools.
• packages/session-ui/src/tools/tool-renderer.tsx — SessionShellMessage renders via ToolRegistry.render("shell") (agent tool-call UI).
• packages/session-ui/src/timeline/detail.ts — timelineDetail shell category and presets (default compact collapses shell).
• packages/app/src/session/timeline/controller.tsx — shellToolPartsExpanded drives shellToolDefaultOpen.

Suggestion

Distinguish user-initiated shell messages from agent shell tool parts:

• Either give user shell messages their own default (expanded) independent of the agent shell collapse setting, or
• Add a separate timeline category / setting (e.g. userShell) with its own placement/details, or
• Render user shell commands with a dedicated, non-collapsed component.

This keeps the existing agent shell tool collapse behavior intact while making user-run commands readable.