fix(build): remove obsolete @lydell/node-pty extraResources entry

The extraResources entry for node_modules/@lydell/node-pty was producing
a "file source doesn't exist" warning during builds because the directory
is empty. This entry was carried over from the migration away from node-pty
(commit e1aee6a4) but is unnecessary for @lydell/node-pty.

Background:
- @lydell/node-pty uses platform-specific optional dependencies
  (@lydell/node-pty-darwin-arm64, -win32-x64, -linux-x64, etc.)
- The base @lydell/node-pty directory contains only metadata, not binaries
- electron-builder automatically detects and handles native .node modules
- The platform-specific packages are included via npm's dependency resolution

Tested: macOS arm64 build works correctly with terminal functionality intact.
The native binaries are properly included in app.asar.unpacked via
electron-builder's automatic native module detection.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/frontend/package.json

@@ -159,10 +159,6 @@
       "package.json"
     ],
     "extraResources": [
-      {
-        "from": "node_modules/@lydell/node-pty",
-        "to": "node_modules/@lydell/node-pty"
-      },
       {
         "from": "resources/icon.ico",
         "to": "icon.ico"