Keep proven external connection failures out of Sentry (#15590)

Apply the reviewed change for Keep proven external connection failures out of Sentry.

Validation: local typecheck/build and focused regression tests, passing exact-head CI, Greptile 5/5, and independent source review. The PR records full-suite evidence and any local environment limitations.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

server/src/middleware/error-handler.ts

@@ -13,6 +13,7 @@ import {
   redactSensitiveValueOccurrences,
 } from "./redact-sensitive.js";
 import { recordResponsibleUserDenialOnActiveRun } from "../services/responsible-user-denial-run-outcomes.js";
+import { isExpectedMcpConnectionFailure } from "../services/mcp-connection-failure.js";
 
 export interface ErrorContext {
   error: {
@@ -85,10 +86,10 @@ function sanitizeSecretSensitiveResponse(
 }
 
 /** Report a server-side crash to every error sink. */
-function reportCrash(error: Error): void {
+function reportCrash(error: Error, reportToSentry = true): void {
   const tc = getTelemetryClient();
   if (tc) trackErrorHandlerCrash(tc, { errorCode: error.name });
-  captureException(error);
+  if (reportToSentry) captureException(error);
 }
 
 function getPaperclipDb(req: Request): Db | null {
@@ -176,7 +177,7 @@ export function errorHandler(
             },
         reportableError,
       );
-      reportCrash(reportableError);
+      reportCrash(reportableError, !isExpectedMcpConnectionFailure(err));
     }
     const secretSensitiveServerError =
       err.status >= 500 &&