chore(turbo): filter test pipeline to packages with tests

turbo run test was building the full workspace graph (including tsconnect,
which requires the tailscale submodule) because example-app and test-app
transitively pull it in via ^build. Scope test and test:coverage to the
three packages that actually have test scripts.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -8,8 +8,8 @@
   ],
   "scripts": {
     "build": "turbo run build",
-    "test": "turbo run test",
-    "test:coverage": "turbo run test:coverage",
+    "test": "turbo run test --filter=@webnet/transport --filter=@webnet/http --filter=@webnet/websocket",
+    "test:coverage": "turbo run test:coverage --filter=@webnet/transport --filter=@webnet/http --filter=@webnet/websocket",
     "lint": "eslint packages/*/src",
     "lint:fix": "eslint packages/*/src --fix",
     "format": "prettier --write \"packages/*/src/**/*.{ts,tsx,js,json}\"",