[Bug] Agent view dispatcher composer remains pinned over attached session, occluding scroll history

Bug Description
Title: Agent view "new session" composer stays pinned over attached session, clipping scroll history (v2.1.197)

Version: Claude Code v2.1.197 (native install, ~/.local/bin/claude)
Platform: macOS (Darwin 25.4.0), iTerm2
Model: Opus 4.8 (1M context)

Summary:
In agent view, after fully attaching to a background session with →/Enter, the "describe a task for a new session" dispatcher composer remains pinned at the top of the screen instead
of being replaced by the session. The session's conversation renders underneath it, so the top rows of history are permanently covered and cannot be scrolled into view.

Steps to reproduce:

1. Launch agent view (claude agents) with several background sessions.
2. Select a worker row and press → (or Enter) to fully attach.
3. Try to scroll the attached session's history up to the beginning.

Expected: Per the docs ("Agent view is replaced by the full interactive session"), the dispatcher composer disappears and the full session history is visible top-to-bottom.

Actual: The ❯ describe a task for a new session composer + enter to open · space to reply · ctrl+x to delete · ? for shortcuts hint bar stays fixed at the top of the attached view.
Conversation history scrolls beneath it, so the earliest messages stay hidden behind the bar.

Workarounds tried (none fixed it):

• claude update — already on latest (2.1.197).
• CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN=1 (classic renderer, tui was fullscreen) — composer still pinned, so the bug is not the alternate-screen buffer.
• PgUp/PgDn scrolling inside Claude Code — top rows remain occluded by the bar.

Impact: Can't read the top of any worker's conversation history in agent view. Reproduces on every worker, every relaunch.

Environment Info

• Platform: darwin
• Terminal: xterm-256color
• Version: 2.1.197
• Feedback ID: 769c6eee-1e08-40b3-8976-2de112de4f0b

Errors

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