Scroll broken (mouse wheel → arrow-key input) for sessions opened via Agents view; persists across terminals on reattach

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) and this hasn't been reported yet
- [x] This is a single bug report (please file separate reports for different bugs)
- [x] I am using the latest version of Claude Code

### What's Wrong?

When a session is opened via the Agents view (the "Needs input / Working / Completed"
dashboard reached via `claude --resume` / `claude --continue` / the in-app Agents screen),
mouse wheel scrolling in that session stops working and is instead interpreted as arrow-key
input (cycling through prompt/input history) rather than scrolling the conversation viewport.

Unlike other reported mouse/scroll bugs, this is not tied to a specific terminal emulator.
Once a session is broken this way:
- It remains broken in a standalone PowerShell window (not just VS Code's integrated terminal).
- It remains broken even in a completely different terminal application.
- Returning to the Agents view and reattaching to the same session reproduces the broken
state again.
- Opening a brand-new session the normal way (not via the Agents view) works correctly and
scrolls fine.

This suggests the broken mouse/scroll state is associated with the session itself (or how
the Agents view attaches to it), not with the terminal host.

### Workaround
Avoid the Agents view; open/resume sessions directly (e.g. `claude --resume `
with an explicit ID) instead of through the dashboard picker.

### Related (not duplicates)
- #61488 — mouse wheel scrolling broken in agent view, converted to arrow-key input
(matches part of this symptom, but doesn't report it persisting across terminal hosts
or being tied to session reattachment)
- #75521 — Agents view (via `--resume`/`--continue`) freezing all keyboard input on macOS
(different symptom, same general area — the Agents view/resume picker)

### What Should Happen?

Mouse wheel should scroll the conversation viewport regardless of whether the session was
opened directly or reattached via the Agents view, and regardless of terminal host.

### Error Messages/Logs

```shell

```

### Steps to Reproduce

1. Start a Claude Code session normally and use it for a while.
2. Return to the Agents view (`claude --resume`, `claude --continue`, or the in-app Agents
screen) and select that session to reattach.
3. Try to scroll the conversation with the mouse wheel.
4. Observe: scroll wheel cycles through input/prompt history instead of scrolling the
conversation viewport.
5. Close that terminal entirely, open a fresh standalone PowerShell window, and reattach to
the same session via the Agents view again.
6. Observe: scrolling is still broken, in a completely different terminal process.
7. Start a brand-new session (not via Agents view) — scrolling works normally.

### Claude Model

Other

### Is this a regression?

I don't know

### Last Working Version

_No response_

### Claude Code Version

2.1.274

### Platform

Anthropic API

### Operating System

Windows

### Terminal/Shell

VS Code integrated terminal

### Additional Information

also recreated this issue in Powershell