♻️ 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/ConnectionsRepository.ts

@@ -4,6 +4,8 @@ import { MCPConnection } from './connection';
 import { MCPServersRegistry } from '~/mcp/registry/MCPServersRegistry';
 import type * as t from './types';
 
+const CONNECT_CONCURRENCY = 3;
+
 /**
  * Manages MCP connections with lazy loading and reconnection.
  * Maintains a pool of connections and handles connection lifecycle management.
@@ -84,9 +86,17 @@ export class ConnectionsRepository {
 
   /** Gets or creates connections for multiple servers concurrently */
   async getMany(serverNames: string[]): Promise<Map<string, MCPConnection>> {
-    const connectionPromises = serverNames.map(async (name) => [name, await this.get(name)]);
-    const connections = await Promise.all(connectionPromises);
-    return new Map((connections as [string, MCPConnection][]).filter((v) => !!v[1]));
+    const results: [string, MCPConnection | null][] = [];
+    for (let i = 0; i < serverNames.length; i += CONNECT_CONCURRENCY) {
+      const batch = serverNames.slice(i, i + CONNECT_CONCURRENCY);
+      const batchResults = await Promise.all(
+        batch.map(
+          async (name): Promise<[string, MCPConnection | null]> => [name, await this.get(name)],
+        ),
+      );
+      results.push(...batchResults);
+    }
+    return new Map(results.filter((v): v is [string, MCPConnection] => v[1] != null));
   }
 
   /** Returns all currently loaded connections without creating new ones */