fix(cli): exorcise the DERP healthcheck demon from TestSupportBundle (#23337)

- Replace real healthcheck with mock `HealthcheckFunc` that returns a
canned report instantly
- Remove healthcheck cache-seeding goroutine/channel workaround
- Remove `HealthcheckTimeout: testutil.WaitSuperLong` (no longer needed)
- Reduce `setupCtx` from `WaitSuperLong` (60s) to `WaitLong` (25s)

The DERP healthcheck performs real network operations (portmapper
gateway probing, STUN) that hang for 60s+ on macOS CI runners. Since
`TestSupportBundle` validates bundle generation, not healthcheck
correctness, a canned report eliminates this entire class of flake.

Fixes coder/internal#272

> 🤖 This PR was created with the help of Coder Agents, and was reviewed
by my human. 🧑‍💻

cli/support_test.go

@@ -28,7 +28,9 @@ import (
 	"github.com/coder/coder/v2/coderd/database/dbauthz"
 	"github.com/coder/coder/v2/coderd/database/dbfake"
 	"github.com/coder/coder/v2/coderd/database/dbtime"
+	"github.com/coder/coder/v2/coderd/healthcheck"
 	"github.com/coder/coder/v2/coderd/healthcheck/derphealth"
+	"github.com/coder/coder/v2/coderd/healthcheck/health"
 	"github.com/coder/coder/v2/codersdk"
 	"github.com/coder/coder/v2/codersdk/agentsdk"
 	"github.com/coder/coder/v2/codersdk/healthsdk"
@@ -50,9 +52,21 @@ func TestSupportBundle(t *testing.T) {
 	dc.Values.Prometheus.Enable = true
 	secretValue := uuid.NewString()
 	seedSecretDeploymentOptions(t, &dc, secretValue)
+	// Use a mock healthcheck function to avoid flaky DERP health
+	// checks in CI. The DERP checker performs real network operations
+	// (portmapper gateway probing, STUN) that can hang for 60s+ on
+	// macOS CI runners. Since this test validates support bundle
+	// generation, not healthcheck correctness, a canned report is
+	// sufficient.
 	client, closer, api := coderdtest.NewWithAPI(t, &coderdtest.Options{
-		DeploymentValues:   dc.Values,
-		HealthcheckTimeout: testutil.WaitSuperLong,
+		DeploymentValues: dc.Values,
+		HealthcheckFunc: func(_ context.Context, _ string, _ *healthcheck.Progress) *healthsdk.HealthcheckReport {
+			return &healthsdk.HealthcheckReport{
+				Time:     time.Now(),
+				Healthy:  true,
+				Severity: health.SeverityOK,
+			}
+		},
 	})
 
 	t.Cleanup(func() { closer.Close() })
@@ -60,7 +74,7 @@ func TestSupportBundle(t *testing.T) {
 	memberClient, member := coderdtest.CreateAnotherUser(t, client, owner.OrganizationID)
 
 	// Set up test fixtures
-	setupCtx := testutil.Context(t, testutil.WaitSuperLong)
+	setupCtx := testutil.Context(t, testutil.WaitLong)
 	workspaceWithAgent := setupSupportBundleTestFixture(setupCtx, t, api.Database, owner.OrganizationID, owner.UserID, func(agents []*proto.Agent) []*proto.Agent {
 		// This should not show up in the bundle output
 		agents[0].Env["SECRET_VALUE"] = secretValue
@@ -69,22 +83,6 @@ func TestSupportBundle(t *testing.T) {
 	workspaceWithoutAgent := setupSupportBundleTestFixture(setupCtx, t, api.Database, owner.OrganizationID, owner.UserID, nil)
 	memberWorkspace := setupSupportBundleTestFixture(setupCtx, t, api.Database, owner.OrganizationID, member.ID, nil)
 
-	// Wait for healthcheck to complete successfully before continuing with sub-tests.
-	// The result is cached so subsequent requests will be fast.
-	healthcheckDone := make(chan *healthsdk.HealthcheckReport)
-	go func() {
-		defer close(healthcheckDone)
-		hc, err := healthsdk.New(client).DebugHealth(setupCtx)
-		if err != nil {
-			assert.NoError(t, err, "seed healthcheck cache")
-			return
-		}
-		healthcheckDone <- &hc
-	}()
-	if _, ok := testutil.AssertReceive(setupCtx, t, healthcheckDone); !ok {
-		t.Fatal("healthcheck did not complete in time -- this may be a transient issue")
-	}
-
 	t.Run("WorkspaceWithAgent", func(t *testing.T) {
 		t.Parallel()