[Bug] Mouse wheel dead in the TUI inside the VS Code integrated terminal since 1.105, root cause is xterm not opencode

Description

The mouse wheel is dead in the TUI inside the VS Code integrated terminal. Arrow keys work, but scrolling the wheel does nothing. This started with VS Code 1.105.

The root cause is not opencode. The wheel events are silently swallowed by xterm.js, the terminal emulator bundled in VS Code, in the alt buffer. The regression was introduced in xterm 5.6.0-beta.119. I verified this with byte-level A/B testing between VS Code 1.104 (beta.118) and 1.105 (beta.119): a raw-mode pty listener plus CDP-injected wheel events. Pixel deltas under roughly 50px produce zero bytes on the pty, so the app never sees them. This affects trackpads, smooth wheels and low-sensitivity mice; fast-scrolling mice can pass the threshold, which is why it is so easy to miss.

Analysis and fix already submitted upstream:

• xterm.js issue with full evidence: https://github.com/xtermjs/xterm.js/issues/6105
• xterm.js fix PR: https://github.com/xtermjs/xterm.js/pull/6104

Opening this here so opencode users hitting it in VS Code have a searchable reference, and a place to pick up the fix once VS Code ships a newer xterm.

Plugins

None

OpenCode version

Latest (dev build), run inside the VS Code integrated terminal

Steps to reproduce

1. VS Code 1.105 or later on Windows, open the integrated terminal
2. Start opencode (TUI)
3. Hover the list and scroll the mouse wheel
4. Trackpad / smooth wheel / low-sensitivity mouse: scroll does nothing

Screenshot and/or share link

Not applicable, see byte-level evidence in the linked xterm.js issue

Operating System

Windows 11

Terminal

VS Code integrated terminal (bundled xterm)