chore(api): remove unused backend endpoints after MCP audit

Remove legacy backend routes that no longer have frontend or internal
callers, including the old Claude/Codex MCP APIs, unused Cursor and Codex
helper endpoints, stale TaskMaster detection/next/initialize routes,
and unused command/project helpers.

This reduces duplicated MCP behavior now handled by the provider-based
MCP API, shrinks the exposed backend surface, and removes probe/service
code that only existed for deleted endpoints.

Add an MCP settings API audit document to capture the route-usage
analysis and explain why the legacy MCP endpoints were considered safe
to remove.

server/modules/providers/services/mcp.service.ts

@@ -60,25 +60,6 @@ export const providerMcpService = {
     return provider.mcp.removeServer(input);
   },
 
-  /**
-   * Runs one provider MCP server probe.
-   */
-  async runProviderMcpServer(
-    providerName: string,
-    input: { name: string; scope?: McpScope; workspacePath?: string },
-  ): Promise<{
-    provider: LLMProvider;
-    name: string;
-    scope: McpScope;
-    transport: 'stdio' | 'http' | 'sse';
-    reachable: boolean;
-    statusCode?: number;
-    error?: string;
-  }> {
-    const provider = providerRegistry.resolveProvider(providerName);
-    return provider.mcp.runServer(input);
-  },
-
   /**
    * Adds one HTTP/stdio MCP server to every provider.
    */