Plan-exit question dock has poor UX: no markdown, no scroll, auto-scroll to bottom, no collapse

[BYK]

Describe the bug

The plan-exit question dock (shown when plan_exit is called to switch from plan to build agent) has several UX issues:

1. Plan content not rendered as markdown — The plan text in the exit prompt is shown as plain text, making it hard to read structured plans with headings, lists, and code blocks.
2. Empty plan not guarded — If the plan is empty, the prompt still shows with no useful content.
3. Question dock text not rendered as markdown — The question text in the web UI dock is plain text rather than markdown.
4. No scroll for long content — When plan content is long, the question dock overflows without a scrollbar.
5. Auto-scroll to focused option — When an option is focused, the dock auto-scrolls to the bottom, making it impossible to read the plan content above.
6. No tap-to-collapse — There is no way to collapse the question dock to see the session content behind it.

Steps to reproduce

1. Enter plan mode and create a long plan
2. Call plan_exit to switch to build agent
3. Observe the question dock: no markdown rendering, no scroll, auto-scrolls away from content

Expected behavior

• Plan content should render as markdown
• Empty plans should be handled gracefully
• Long content should be scrollable
• Focus should not auto-scroll away from content
• Dock should be collapsible by tapping the header

System info

• OpenCode version: v1.15.3
• OS: Linux

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Planning mode: subagents can trigger plan_exit, plan not shown before build switch, question text renders as plain text #18515: Covers overlapping bugs — plan content not shown before build switch, question text renders as plain text (points 1 and 3 of this issue)
• [FEATURE] Add collapse/expand functionality to question tool dialog #19400: Covers the collapse/expand functionality for the question dock (point 6 of this issue)

You may want to consider whether this issue should reference or be merged with those existing reports, or clarify which aspects are not already tracked there.

[BYK]

Thanks for flagging — #18515 covers the same bugs. PR #27890 addresses points 2 and 3 from that issue (plan content as markdown + question text rendering). Point 1 (subagent escape) is addressed by PR #27887.