feat: ship the ssh terminal as a first-party in-process plugin

Adds a hardcoded process:transport-owner tier so the terminal can own its
WebSocket server and ssh2 clients, which cannot cross the worker boundary.

electron-builder.json

@@ -8,6 +8,7 @@
   "asar": true,
   "asarUnpack": [
     "dist/backend/**/*",
+    "dist/plugins/**/*",
     "node_modules/**/*",
     "public/icons/**/*",
     "public/icon.*"