[Fix] Session prompt loses focus when task panels expand

[roomote-roomote]

​Created by Roomote. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

What changed

• Keep focus on the main Session prompt when task panels expand automatically on load, when newly delegated tasks appear, or when tasks are opened side by side.
• Continue focusing a task prompt when its task card is explicitly selected.
• Add regression coverage for automatic expansion, the side-by-side action, explicit task-card selection, and existing keyboard focus navigation.

Why this change was made

Expanding task panels reused the explicit task-selection focus path, unexpectedly moving users away from the Session composer even though they had not selected a task.

Impact

Sessions can display running tasks side by side without interrupting typing in the main prompt. Direct task selection and Alt/Option + Arrow prompt navigation retain their existing behavior.

[roomote-community]

1 issue outstanding. See task

• Side-by-side opening does not preserve Session composer focus for a real pointer click. (apps/web/src/app/(sandbox)/sessions/[sessionId]/use-session-workspace-panels.ts:211)

_{Reviewed 7b3610d}

[roomote-community]

Opening side-by-side from the native Button moves browser focus to that button before this reducer runs. This action now removes the task-focus request but never restores the Session composer, so a real pointer click still interrupts typing (the new fireEvent.click test does not emulate native focus transfer). Preserve the existing prompt focus on pointer activation, or explicitly restore it after the panels mount.