feat(deepnote-server): Improve error handling for IPv6 checks

Signed-off-by: Tomas Kislan <tomas@kislan.sk>

Author: tkislan

src/kernels/deepnote/deepnoteServerStarter.node.ts

@@ -624,8 +624,8 @@ export class DeepnoteServerStarter implements IDeepnoteServerStarter, IExtension
             try {
             const inUseIpv6 = await tcpPortUsed.check(port, '::1');
             return !inUseIpv6;
-            } catch (error) {
-                if (error instanceof Error && error.message.includes('EAFNOSUPPORT')) {
+            } catch (error: unknown) {
+                if (error instanceof Error && 'code' in error && error.code === 'EAFNOSUPPORT') {
                     logger.debug('IPv6 is not supported on this system');
                     return true;
                 }

src/kernels/deepnote/deepnoteServerStarter.unit.test.ts

@@ -120,6 +120,7 @@ suite('DeepnoteServerStarter - Port Allocation Integration Tests', () => {
         test('should return true when IPv6 is disabled (EAFNOSUPPORT error)', async () => {
             const port = 54324;
             const ipv6Error = new Error('connect EAFNOSUPPORT ::1:54324');
+            (ipv6Error as any).code = 'EAFNOSUPPORT';
 
             // IPv4 check succeeds (port is available)
             checkStub.onFirstCall().resolves(false);