Fix flaky gRPC renewal test timing

Increase token lifetime from 2s to 4s in TestRenewToken to prevent
the token from expiring before the gRPC call completes through bufconn.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/grpcserver/grpcserver_test.go

@@ -370,11 +370,11 @@ func TestRenewToken(t *testing.T) {
 	e := newTestEnv(t)
 	acct := e.createHumanAccount(t, "renewuser")
 
-	// Issue a short-lived token (2s) so we can wait past the 50% threshold.
-	tok := e.issueShortToken(t, acct, 2*time.Second)
+	// Issue a short-lived token (4s) so we can wait past the 50% threshold.
+	tok := e.issueShortToken(t, acct, 4*time.Second)
 
 	// Wait for >50% of lifetime to elapse.
-	time.Sleep(1100 * time.Millisecond)
+	time.Sleep(2100 * time.Millisecond)
 
 	cl := mciasv1.NewAuthServiceClient(e.conn)
 	ctx := authCtx(tok)