Fix crxjs dev service worker crashes after Vite upgrade.

Downgrade to Vite 6 with crxjs 2.6, add dev-only CSP for HMR, and stop the background script from importing Svelte plugin UI into the service worker.

package.json

@@ -42,7 +42,7 @@
     "@babel/plugin-transform-runtime": "^7.26.9",
     "@babel/runtime": "^7.26.9",
     "@bedframe/cli": "^0.1.2",
-    "@crxjs/vite-plugin": "^2.4.0",
+    "@crxjs/vite-plugin": "^2.6.1",
     "@types/d3-scale": "^4.0.9",
     "@types/d3-shape": "^3.1.8",
     "@types/jest": "^30.0.0",
@@ -77,7 +77,7 @@
     "@codemirror/search": "^6.5.10",
     "@codemirror/state": "^6.5.2",
     "@codemirror/view": "^6.36.4",
-    "@sveltejs/vite-plugin-svelte": "^7.0.0",
+    "@sveltejs/vite-plugin-svelte": "^5.0.3",
     "@tailwindcss/forms": "^0.5.10",
     "@tsconfig/svelte": "^5.0.4",
     "@types/chrome": "^0.1.4",
@@ -122,7 +122,7 @@
     "svelte": "^5.46.4",
     "typescript": "^5.8.2",
     "uuid": "^11.1.0",
-    "vite": "^8.0.5",
+    "vite": "^6.2.1",
     "webextension-polyfill": "^0.12.0"
   }
 }