fix: revert premature isConnecting reset + remove popup disconnected flicker

- background.js: remove isConnecting=false at line 608 (was set before
  WebSocket handshake completed, defeating the guard for the entire
  CONNECTING phase). isConnecting is already properly reset in onclose,
  onopen/40 handler, catch block, and socket guard path.
- background.js: restore isConnecting=false in forceDisconnect() so
  subsequent connect() calls can proceed after intentional disconnect.
- popup.js: remove hardcoded applyConnectionStatus('disconnected') that
  caused a guaranteed red flicker on every popup open. Status is now
  set only by the async GET_STATUS response.

extension/background.js

@@ -343,6 +343,7 @@ function forceDisconnect() {
         socket = null;
     }
     currentServerUrl = null;
+    isConnecting = false;
     isNamespaceJoined = false;
     isForceSyncInitiator = false;
     expectedAcksCount = 0;
@@ -605,8 +606,6 @@ async function connect() {
             addLog('WebSocket Error: Connection failed', logType);
         };
 
-        isConnecting = false;
-
     } catch (e) {
         isConnecting = false;
         const logType = reconnectAttempts > 1 ? 'error' : 'warn';

extension/popup.js

@@ -237,8 +237,7 @@ async function init() {
     refreshLogs();
     refreshHistory();
 
-    // Default connection status (localized) before async check
-    applyConnectionStatus('disconnected');
+    // Initial Status Check (status shows via GET_STATUS below)
 
     // Initial Status Check
     chrome.runtime.sendMessage({ type: 'GET_STATUS' }, async (res) => {