Add grok.com; fix fetch hook on React/Next.js sites (Reddit, Grok, etc.)

Two fixes:

1. grok.com missing from manifest
   Grok moved from grok.x.ai to grok.com. The extension wasn't activating
   on grok.com at all (no content script injected). Added to host_permissions
   and content_scripts in both manifests.

2. Fetch hook bypassed on React/Next.js sites
   content.js was injected async (after awaiting the document-scanner),
   so by the time it replaced window.fetch, React/Next.js had already stored
   a reference to the original. All fetch calls from framework code bypassed
   the hook entirely.

   Fix: load early-hook.js as a "world": "MAIN" content script at
   document_start. This runs synchronously before any page JavaScript,
   captures the real fetch in window.__ssOriginalFetch, and replaces
   window.fetch with a lightweight wrapper. When content.js eventually
   loads, it sets window.__ssInterceptFetch (the real substitution logic)
   and window.__ssReady = true, activating the wrapper. React's stored
   fetch reference now routes through the interceptor.

   Falls back to direct window.fetch replacement if early-hook.js somehow
   didn't run (e.g. older browser without world: MAIN support).

https://claude.ai/code/session_01CwcZK8nqL8pyBH9AxDs9qo

manifest.firefox.json

@@ -25,6 +25,7 @@
     "https://chatgpt.com/*",
     "https://chat.openai.com/*",
     "https://copilot.microsoft.com/*",
+    "https://grok.com/*",
     "https://grok.x.ai/*",
     "https://x.com/i/grok*",
     "https://gemini.google.com/*",
@@ -53,6 +54,36 @@
         "https://chatgpt.com/*",
         "https://chat.openai.com/*",
         "https://copilot.microsoft.com/*",
+        "https://grok.com/*",
+        "https://grok.x.ai/*",
+        "https://x.com/i/grok*",
+        "https://gemini.google.com/*",
+        "https://www.perplexity.ai/*",
+        "https://copilot.microsoft.com/*",
+        "https://chat.deepseek.com/*",
+        "https://huggingface.co/chat/*",
+        "https://poe.com/*",
+        "https://github.com/*",
+        "https://gitlab.com/*",
+        "https://www.reddit.com/*",
+        "https://old.reddit.com/*",
+        "https://stackoverflow.com/*",
+        "https://pastebin.com/*",
+        "http://localhost/*",
+        "http://127.0.0.1/*"
+      ],
+      "js": ["src/content/early-hook.js"],
+      "run_at": "document_start",
+      "world": "MAIN",
+      "all_frames": true
+    },
+    {
+      "matches": [
+        "https://claude.ai/*",
+        "https://chatgpt.com/*",
+        "https://chat.openai.com/*",
+        "https://copilot.microsoft.com/*",
+        "https://grok.com/*",
         "https://grok.x.ai/*",
         "https://x.com/i/grok*",
         "https://gemini.google.com/*",
@@ -114,7 +145,7 @@
   ],
   "web_accessible_resources": [
     {
-      "resources": ["src/content/content.js", "src/content/early-hook.js", "src/lib/document-scanner.js"],
+      "resources": ["src/content/content.js", "src/lib/document-scanner.js"],
       "matches": ["<all_urls>"]
     }
   ]