fix: add missing return after exitWithNoMatchingRequestError in CI mode

When running tests in CI mode with no cached response, the proxy would
crash with ERR_HTTP_HEADERS_SENT because exitWithNoMatchingRequestError()
calls onError() (which writes headers), but then execution continued to
super.performRequest() which also tries to write headers.

This caused cascading test failures because the proxy process would die
and subsequent tests couldn't communicate with it.

This is why the 'sendAndWait throws on timeout' test is currently
skipped in CI. With this fix, that test could potentially be enabled.

Author: brunoborges

test/harness/replayingCapiProxy.ts

@@ -292,6 +292,7 @@ export class ReplayingCapiProxy extends CapturingHttpProxy {
             state.workDir,
             state.toolResultNormalizers,
           );
+          return;
         }
         super.performRequest(options);
       } catch (err) {