♻️ 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.

api/server/controllers/AuthController.js

@@ -18,7 +18,6 @@ const {
   findUser,
 } = require('~/models');
 const { getGraphApiToken } = require('~/server/services/GraphTokenService');
-const { getOAuthReconnectionManager } = require('~/config');
 const { getOpenIdConfig } = require('~/strategies');
 
 const registrationController = async (req, res) => {
@@ -166,17 +165,6 @@ const refreshController = async (req, res) => {
     if (session && session.expiration > new Date()) {
       const token = await setAuthTokens(userId, res, session);
 
-      // trigger OAuth MCP server reconnection asynchronously (best effort)
-      try {
-        void getOAuthReconnectionManager()
-          .reconnectServers(userId)
-          .catch((err) => {
-            logger.error('[refreshController] Error reconnecting OAuth MCP servers:', err);
-          });
-      } catch (err) {
-        logger.warn(`[refreshController] Cannot attempt OAuth MCP servers reconnection:`, err);
-      }
-
       res.status(200).send({ token, user });
     } else if (req?.query?.retry) {
       // Retrying from a refresh token request that failed (401)