feat(FN-3396): bundle Cursor CLI as a plugin provider with dashboard auth w

Merges FN-3396's full Cursor CLI provider integration (Steps 1–4): defines a CLI-backed provider contract, adds the `fusion-plugin-cursor-runtime` plugin package with process management and runtime probes, wires dashboard auth flows and UI (ProviderCard, onboarding modal, settings), and bundles the

Fusion-Task-Id: FN-3396

plugins/fusion-plugin-cursor-runtime/manifest.json

@@ -0,0 +1,6 @@
+{
+  "id": "fusion-plugin-cursor-runtime",
+  "name": "Cursor Runtime Plugin",
+  "version": "0.1.0",
+  "description": "Provides Cursor CLI-backed model provider and runtime integration"
+}