fix(kthread_stress): align build with boot_stages configuration

- Add external_test_bins to kthread_stress_test feature to match
  boot_stages build configuration
- Update xtask to create test disk before running stress test

This ensures the kthread stress test kernel is compiled the same way
as the boot stages kernel, which should help with any timing-sensitive
issues related to code layout.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: ryanbreen

kernel/Cargo.toml

@@ -19,7 +19,7 @@ test = false
 [features]
 testing = []
 kthread_test_only = ["testing"]  # Run only kthread tests and exit
-kthread_stress_test = ["testing"]  # Run kthread stress test (100+ kthreads) and exit
+kthread_stress_test = ["testing", "external_test_bins"]  # Run kthread stress test (100+ kthreads) and exit
 workqueue_test_only = ["testing"]  # Run only workqueue tests and exit
 test_divide_by_zero = []
 test_invalid_opcode = []

xtask/src/main.rs

@@ -2888,6 +2888,15 @@ fn kthread_stress() -> Result<()> {
 fn kthread_stress_ci() -> Result<()> {
     println!("=== Kthread Stress Test (CI mode) ===\n");
 
+    // Build std test binaries BEFORE creating the test disk
+    // This ensures hello_std_real is available to be included
+    build_std_test_binaries()?;
+
+    // Create the test disk with all userspace binaries
+    // Required since kthread_stress_test now includes external_test_bins
+    test_disk::create_test_disk()?;
+    println!();
+
     // COM1 (user output) and COM2 (kernel logs) - stress test markers go to COM2
     let user_output_file = "target/kthread_stress_user.txt";
     let serial_output_file = "target/kthread_stress_output.txt";