Astro Bot stack: VEH/TBB, title clear, swapchain fallback, Psml MFSR (#528)

* Cpu/Kernel: harden VEH trampoline and keep TBB on native workers

Route FastFail/CLR/stack-overflow around managed VEH, serialize managed
entry with a recursive spinlock, require native workers for tbb_thead,
and abandon pthread mutexes when a guest thread is torn down by worker
abort so splash waiters are not left holding locks forever.

* Cpu: soft-fail TBB native worker storms and cap concurrent Runs

Throwing on worker/prologue faults killed the process mid tbb_thead
burst (FailFast 0xC0000409). Soft-return 0x80020012, limit in-flight
native Runs (default 2), and keep prewarm small so back-to-back boots
do not need an artificial settle delay.

* Agc/VideoOut: poison-only empty-SRT reject and clear procedural ES/PS

Skip QueueSubmit only when Address-0 image slots remain; run the
Astro title clear pair via CmdClearColorImage so the pass executes
without descriptors that lose the device.

* VideoOut: recreate swapchain with fallback extent on 0x0 surface

Minimized Win32 surfaces report 0x0 / MaxImageExtent=0; deferring
recreate forever left an OutOfDate swapchain with no presents.
Clamp to last/default size and recreate instead of early-return.

* Psml: stub MFSR init/shared/context and dispatch packet size

Astro Bot asserts in GfxRenderStagePSSR when scePsmlMfsrInit is unresolved
(Mfsr initialized failed). Soft HLE for the MFSR shared-resource and
800M3_2 context path plus dispatch packet size lets boot pass splash to
first frame without claiming real upscaling.

* Psml: stub MFSR GetDispatchMfsrPacket900 for logo PSSR

Astro StartLevel ps_logo asserted GfxRenderStagePSSR.cpp:266 when
GetDispatchMfsrPacket900 (RUNLFro+qok) was unresolved. Return SCE_OK
from SizeInDwords so the 900 fill runs, soft-clear the guest packet
buffer, and register 1000/1100 siblings for the same ABI.

src/SharpEmu.HLE/GuestThreadExecution.cs

@@ -221,6 +221,29 @@ public static class GuestThreadExecution
 
     public static IGuestThreadScheduler? Scheduler { get; set; }
 
+    /// <summary>
+    /// Fired when a guest thread is torn down without a clean pthread_exit
+    /// (e.g. TBB execute-AV → worker_abort). Libs use this to abandon mutexes.
+    /// </summary>
+    public static event Func<ulong, string, int>? GuestThreadAbandoned;
+
+    public static int NotifyGuestThreadAbandoned(ulong threadHandle, string reason)
+    {
+        if (threadHandle == 0 || GuestThreadAbandoned is null)
+        {
+            return 0;
+        }
+
+        try
+        {
+            return GuestThreadAbandoned.Invoke(threadHandle, reason);
+        }
+        catch
+        {
+            return 0;
+        }
+    }
+
     public static bool IsGuestThread => _currentGuestThreadHandle != 0;
 
     public static ulong CurrentGuestThreadHandle => _currentGuestThreadHandle;