Fix Firefox install: use background.scripts instead of service_worker

Firefox MV3 does not support background.service_worker. Split background
into background-boot.js (globals) and background-main.js (startup logic);
Chrome keeps using importScripts() in background.js, Firefox manifest uses
background.scripts with the same file list so the extension loads in both.

extension/background.js

@@ -1,54 +1,14 @@
 /**
- * Background service worker entry point.
+ * Background service worker entry point (Chrome).
- * Loads modules in dependency order via importScripts().
+ * Loads boot globals, then modules, then main logic via importScripts().
  */
-
-const SW_VERSION = 3; // increment to force service worker reload detection
-
-/** Set to true for super detailed debug logging. */
-const DEBUG_VERBOSE = false;
-
-const browser = (typeof chrome !== 'undefined' && chrome.runtime?.connectNative)
-  ? chrome
-  : (globalThis.browser ?? chrome);
-
 importScripts(
+  'background/background-boot.js',
   'background/logs.js',
   'background/state.js',
   'background/proxy.js',
   'background/native-messaging.js',
   'background/tab-lifecycle.js',
-  'background/message-router.js'
+  'background/message-router.js',
+  'background/background-main.js'
 );
-
-log('background: SW started v' + SW_VERSION);
-
-// Apply PAC immediately on startup using default port; updated once native host connects
-applyPAC();
-connect();
-
-// Redirect *.host.test (and similar typos) to extension page so we can show "use .hole.sail"
-const WRONG_DOMAIN_RULE_ID = 1;
-if (browser.declarativeNetRequest && browser.runtime.getURL) {
-  const redirectUrl = browser.runtime.getURL('wrong-domain.html') + '?host=\\1';
-  browser.declarativeNetRequest.updateDynamicRules({
-    removeRuleIds: [WRONG_DOMAIN_RULE_ID],
-    addRules: [{
-      id: WRONG_DOMAIN_RULE_ID,
-      priority: 1,
-      condition: {
-        regexFilter: '^https?://([^/:]+)\\.host\\.test($|/)',
-        resourceTypes: ['main_frame']
-      },
-      action: {
-        type: 'redirect',
-        redirect: { regexSubstitution: redirectUrl }
-      }
-    }]
-  }).catch((err) => log('declarativeNetRequest rule failed:', err.message));
-}
-
-// Open dashboard when extension icon is clicked
-browser.action?.onClicked?.addListener((tab) => {
-  browser.tabs.create({ url: 'dashboard/dashboard.html' });
-});

extension/background/background-boot.js

@@ -0,0 +1,12 @@
+/**
+ * Boot globals for background (shared by service worker and Firefox scripts context).
+ * Loaded first so DEBUG_VERBOSE and browser are available to logs.js and others.
+ */
+const SW_VERSION = 3; // increment to force service worker reload detection
+
+/** Set to true for super detailed debug logging. */
+const DEBUG_VERBOSE = false;
+
+const browser = (typeof chrome !== 'undefined' && chrome.runtime?.connectNative)
+  ? chrome
+  : (globalThis.browser ?? chrome);

extension/background/background-main.js

@@ -0,0 +1,35 @@
+/**
+ * Background main logic (after all modules loaded).
+ * Used by both Chrome (via importScripts from background.js) and Firefox (via background.scripts).
+ */
+log('background: SW started v' + SW_VERSION);
+
+// Apply PAC immediately on startup using default port; updated once native host connects
+applyPAC();
+connect();
+
+// Redirect *.host.test (and similar typos) to extension page so we can show "use .hole.sail"
+const WRONG_DOMAIN_RULE_ID = 1;
+if (browser.declarativeNetRequest && browser.runtime.getURL) {
+  const redirectUrl = browser.runtime.getURL('wrong-domain.html') + '?host=\\1';
+  browser.declarativeNetRequest.updateDynamicRules({
+    removeRuleIds: [WRONG_DOMAIN_RULE_ID],
+    addRules: [{
+      id: WRONG_DOMAIN_RULE_ID,
+      priority: 1,
+      condition: {
+        regexFilter: '^https?://([^/:]+)\\.host\\.test($|/)',
+        resourceTypes: ['main_frame']
+      },
+      action: {
+        type: 'redirect',
+        redirect: { regexSubstitution: redirectUrl }
+      }
+    }]
+  }).catch((err) => log('declarativeNetRequest rule failed:', err.message));
+}
+
+// Open dashboard when extension icon is clicked
+browser.action?.onClicked?.addListener((tab) => {
+  browser.tabs.create({ url: 'dashboard/dashboard.html' });
+});

extension/manifest_firefox.json

@@ -29,7 +29,16 @@
     }
   },
   "background": {
-    "service_worker": "background.js"
+    "scripts": [
+      "background/background-boot.js",
+      "background/logs.js",
+      "background/state.js",
+      "background/proxy.js",
+      "background/native-messaging.js",
+      "background/tab-lifecycle.js",
+      "background/message-router.js",
+      "background/background-main.js"
+    ]
   },
   "content_scripts": [
     {