♻️ refactor: On-demand MCP connections: remove proactive reconnect, default to available (#11839)

* feat: Implement reconnection staggering and backoff jitter for MCP connections

- Enhanced the reconnection logic in OAuthReconnectionManager to stagger reconnection attempts for multiple servers, reducing the risk of connection storms.
- Introduced a backoff delay with random jitter in MCPConnection to improve reconnection behavior during network issues.
- Updated the ConnectionsRepository to handle multiple server connections concurrently with a defined concurrency limit.

Added tests to ensure the new reconnection strategy works as intended.

* refactor: Update MCP server query configuration for improved data freshness

- Reduced stale time from 5 minutes to 30 seconds to ensure quicker updates on server initialization.
- Enabled refetching on window focus and mount to enhance data accuracy during user interactions.

* ♻️  refactor: On-demand MCP connections; remove proactive reconnection, default to available

  - Remove reconnectServers() from refresh controller (connection storm root cause)
  - Stop gating server selection on connection status; add to selection immediately
  - Render agent panel tools from DB cache, not live connection status
  - Proceed to cached tools on init failure (only gate on OAuth)
  - Remove unused batchToggleServers()
  - Reduce useMCPServersQuery staleTime from 5min to 30s, enable refetchOnMount/WindowFocus

* refactor: Optimize MCP tool initialization and server connection logic

- Adjusted tool initialization to only occur if no cached tools are available, improving efficiency.
- Updated comments for clarity on server connection and tool fetching processes.
- Removed unnecessary connection status checks during server selection to streamline the user experience.

packages/api/src/mcp/oauth/OAuthReconnectionManager.ts

@@ -7,6 +7,7 @@ import { MCPManager } from '~/mcp/MCPManager';
 import { MCPServersRegistry } from '~/mcp/registry/MCPServersRegistry';
 
 const DEFAULT_CONNECTION_TIMEOUT_MS = 10_000; // ms
+const RECONNECT_STAGGER_MS = 500; // ms between each server reconnection
 
 export class OAuthReconnectionManager {
   private static instance: OAuthReconnectionManager | null = null;
@@ -84,9 +85,14 @@ export class OAuthReconnectionManager {
       this.reconnectionsTracker.setActive(userId, serverName);
     }
 
-    // 3. attempt to reconnect the servers
-    for (const serverName of serversToReconnect) {
-      void this.tryReconnect(userId, serverName);
+    // 3. attempt to reconnect the servers with staggered delays to avoid connection storms
+    for (let i = 0; i < serversToReconnect.length; i++) {
+      const serverName = serversToReconnect[i];
+      if (i === 0) {
+        void this.tryReconnect(userId, serverName);
+      } else {
+        setTimeout(() => void this.tryReconnect(userId, serverName), i * RECONNECT_STAGGER_MS);
+      }
     }
   }