fix: add web_accessible_resources for interceptors.js in manifest.json

Without this, Chrome blocks chrome.runtime.getURL('interceptors.js')
in Manifest V3, causing HLS detection to silently fail.

Added regression test to prevent future removal.

manifest.json

@@ -31,6 +31,12 @@
       "all_frames": true
     }
   ],
+  "web_accessible_resources": [
+    {
+      "resources": ["interceptors.js"],
+      "matches": ["<all_urls>"]
+    }
+  ],
   "icons": {
     "16": "icons/icon16.png",
     "48": "icons/icon48.png",