Double-click to select text is broken

[nedtwigg]

• For a terminal which is not capturing mouse input
• When the user clicks and drags, it triggers our special drag-and-drop behavior which works great
• But when the user double-clicks, it triggers some underlying text-selection (not ours). It doesn't look like the text selection above, and Cmd+C doesn't do a copy of the selected text

[dormouse-bot]

Thanks for filing. I dug into the code — what's happening is that xterm.js's built-in double-click word-select is leaking through.

The mouse router in lib/src/lib/terminal-mouse-router.ts only consumes the native mousedown when mouse reporting is active (suppressNativeMouse). With reporting off, xterm.js's own handlers run; its built-in double-click-to-select-word kicks in, paints xterm's native selection rendering (the different look), and Dormouse's mouseSelectionState.selection stays null — so Cmd+C isn't intercepted as Copy Raw (see mouse-and-clipboard.md §4.2).

This also matches the spec's "Out of Scope" list at mouse-and-clipboard.md §9.1: "Double-click to select word, triple-click to select line" — so the proper Dormouse behavior on double-click isn't implemented yet, and xterm's default is what shows up instead. Two possible directions:

1. Implement double-click → Dormouse word-select (and triple-click → line), populating mouseSelectionState.selection so the popup and Cmd+C work the same as drag selection.
2. As a stopgap, suppress xterm's native mousedown even when reporting is off, so the inconsistent xterm selection visual doesn't appear.

Happy to take a stab at (1) if you'd like — wanted to confirm the direction before writing it, since the spec change is part of it.