feat(site): suppress the web terminal context menu when the application has enabled mouse tracking

Inizia in site/src/modules/terminal/WorkspaceTerminal.tsx e ispeziona la gestione di contextmenu del wrapper del terminale, il valore xterm terminal.modes.mouseTrackingMode e il Radix ContextMenuTrigger. Verifica che l'input del mouse tracciato sopprima sia i menu nativi sia quelli di Radix, mentre le shell ordinarie mantengano il comportamento del menu specifico della piattaforma.

Problem

When a TUI that uses mouse reporting (e.g. a coder_app with command = "herdr") runs in the web terminal on macOS, right-clicking opens the browser's native context menu on top of the TUI's own menu. xterm.js forwards the button-3 press to the PTY, so the application handles the click, but nothing suppresses the contextmenu event and the browser menu appears as well.

This is a consequence of a deliberate choice in #26015: site/src/modules/terminal/WorkspaceTerminal.tsx wraps xterm in a Radix ContextMenu with <ContextMenuTrigger asChild disabled={isMac()}>. Windows/Linux get the custom Copy/Paste menu; macOS keeps the native menu because native copy/paste already works there. That is the right default for a plain shell, but wrong when the running application has taken over the mouse. Note the Radix menu on Windows/Linux has the same problem: it opens over the TUI's menu.

There is no escape sequence an application can send to change this; it has to be handled in the frontend.

Proposal

Only show a context menu (native or Radix) when the application has not enabled mouse tracking. xterm.js exposes this via terminal.modes.mouseTrackingMode ('none' | 'x10' | 'vt200' | 'drag' | 'any').

In WorkspaceTerminal.tsx:

• On contextmenu on the terminal wrapper, if terminal.modes.mouseTrackingMode !== 'none', call preventDefault() and let xterm forward the event to the PTY (all platforms).
• Otherwise keep the current behaviour: native menu on macOS, Radix Copy/Paste menu elsewhere. For the Radix path this means gating the trigger on mouse tracking as well, not just isMac().

This matches what VS Code and most desktop terminals do, and keeps the copy/paste affordance for regular shells.

Context

Raised by a customer running a TUI as a coder_app command app whose users are on macOS.

Related: #26015 (custom copy/paste menu), #29564 (per-app icon for the terminal page).

Filed by Coder Agents on behalf of @ericpaulsen.