Replaces the no-op stub at xam.rs:204 with a canary-faithful
implementation mirroring xenia-canary/src/xenia/kernel/xam/xam_task.cc:43-80.
Allocates a ThreadImage, allocates a KernelObject::Thread handle, and
routes through Scheduler::spawn with entry=callback and
start_context=message_ptr (canary's third positional XThread ctor arg).
Stack size = max(0x4000, page-aligned 0x10_0000).
Producer-hypothesis outcome (500M --trace-handles-focus run): the call
site at 0x824a9a10 is never reached during this boot horizon, so
XamTaskSchedule cannot be the missing producer for the 3 parked
Event/Manual handles (0x1004, 0x100c, 0x15e4). The fix still lands —
the stub was a real correctness bug that would manifest the moment
the boot advances past the current deadlock. Next candidate per
audit-findings.md: XAudioRegisterRenderDriverClient.
- Workspace tests: 561 → 562 green (new test
xam::tests::xam_task_schedule_spawns_real_thread).
- --stable-digest -n 100M: instructions=100000002 unchanged from
baseline; lockstep determinism preserved.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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