fix: let nested-KVM vmlaunch succeed with Virtual NMIs

Self-test and Linux guest were failing VM-instruction error 7. Share a KVM-style control adjust, request PIN_VIRTUAL_NMIS, and stop intercepting guest #PF. Land isolated XNU/Python/KDE scaffolding off the boot path.

Co-authored-by: Cursor <cursoragent@cursor.com>

CODE/UTSM/sched/sched_stub.c

@@ -0,0 +1,65 @@
+/*
+ * Isolated scheduler placeholder.
+ *
+ * Deliberately not linked by the UTSM build. These functions make accidental
+ * use fail explicitly until the per-CPU bitmap scheduler and switch path are
+ * implemented.
+ */
+
+#include <utsm/sched.h>
+
+int utsm_sched_init(void) {
+    return UTSM_SCHED_ERR_UNSUPPORTED;
+}
+
+int utsm_sched_cpu_init(u32 cpu_id, utsm_sched_run_queue *queue) {
+    UTSM_UNUSED(cpu_id);
+    UTSM_UNUSED(queue);
+    return UTSM_SCHED_ERR_UNSUPPORTED;
+}
+
+int utsm_sched_task_init(utsm_sched_tcb *task, u64 task_id,
+                         u32 process_slot, u32 priority, u64 affinity_mask) {
+    UTSM_UNUSED(task);
+    UTSM_UNUSED(task_id);
+    UTSM_UNUSED(process_slot);
+    UTSM_UNUSED(priority);
+    UTSM_UNUSED(affinity_mask);
+    return UTSM_SCHED_ERR_UNSUPPORTED;
+}
+
+int utsm_sched_enqueue(u32 cpu_id, utsm_sched_tcb *task) {
+    UTSM_UNUSED(cpu_id);
+    UTSM_UNUSED(task);
+    return UTSM_SCHED_ERR_UNSUPPORTED;
+}
+
+int utsm_sched_dequeue(utsm_sched_tcb *task) {
+    UTSM_UNUSED(task);
+    return UTSM_SCHED_ERR_UNSUPPORTED;
+}
+
+int utsm_sched_block(utsm_sched_tcb *task, u32 blocked_state) {
+    UTSM_UNUSED(task);
+    UTSM_UNUSED(blocked_state);
+    return UTSM_SCHED_ERR_UNSUPPORTED;
+}
+
+int utsm_sched_wake(utsm_sched_tcb *task) {
+    UTSM_UNUSED(task);
+    return UTSM_SCHED_ERR_UNSUPPORTED;
+}
+
+int utsm_sched_pick_next(u32 cpu_id, utsm_sched_tcb **out_task) {
+    UTSM_UNUSED(cpu_id);
+    UTSM_UNUSED(out_task);
+    return UTSM_SCHED_ERR_UNSUPPORTED;
+}
+
+int utsm_sched_tick(u32 cpu_id, u64 elapsed_ns,
+                    utsm_sched_tcb **out_preempted_task) {
+    UTSM_UNUSED(cpu_id);
+    UTSM_UNUSED(elapsed_ns);
+    UTSM_UNUSED(out_preempted_task);
+    return UTSM_SCHED_ERR_UNSUPPORTED;
+}