Enable kitty keyboard protocol so Shift+Enter is distinguishable

In a stock xterm.js terminal, Shift+Enter and Enter both send `\r`, so
TUIs like Claude Code can't bind them differently and both submit.
Upgrading @xterm/xterm to a 6.1.0 beta and opting into
`vtExtensions.kittyKeyboard` lets the terminal advertise the kitty
keyboard protocol; when the inner program negotiates it, modified keys
round-trip as distinct CSI u sequences.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: nedtwigg

lib/package.json

@@ -15,8 +15,8 @@
   },
   "dependencies": {
     "@phosphor-icons/react": "^2.1.10",
-    "@xterm/addon-fit": "^0.11.0",
-    "@xterm/xterm": "^6.0.0",
+    "@xterm/addon-fit": "0.12.0-beta.216",
+    "@xterm/xterm": "6.1.0-beta.216",
     "clsx": "^2.1.1",
     "dockview-react": "^5.1.0",
     "react": "^19.2.0",

lib/src/lib/terminal-lifecycle.ts

@@ -54,6 +54,7 @@ function createXtermHost(): { terminal: Terminal; fit: FitAddon; element: HTMLDi
     fontFamily: editorFontFamily,
     cursorBlink: true,
     theme,
+    vtExtensions: { kittyKeyboard: true },
   });
 
   const fit = new FitAddon();

pnpm-lock.yaml

@@ -15,8 +15,8 @@
     "@tauri-apps/api": "^2.0.0",
     "@tauri-apps/plugin-shell": "^2.0.0",
     "@tauri-apps/plugin-updater": "^2.10.1",
-    "@xterm/addon-fit": "^0.11.0",
-    "@xterm/xterm": "^6.0.0",
+    "@xterm/addon-fit": "0.12.0-beta.216",
+    "@xterm/xterm": "6.1.0-beta.216",
     "dockview-react": "^5.1.0",
     "mouseterm-lib": "workspace:*",
     "react": "^19.0.0",