Astro Bot shader type 4, pthread_cond_timedwait, and HLE/memory/cpu bug fixes (#40)

* [agc] Add shader type 4 (GS) and register defaults v13 support

Astro Bot (#11) crashes on boot due to two missing GPU features:

1. Shader type 4 (Geometry Shader) — SPI_SHADER_PGM_LO/HI register
   offsets 0x8A/0x8B were missing. Added constants and switch cases
   for shader type 4 in GetExpectedSpiShaderPgmLo/Hi. Also added
   type 4 to IsEsGeometryShaderType (2 or 4 or 6).

2. Register defaults version 13 — was not recognized as supported.
   Added RegisterDefaultsVersion13 constant and included it in
   IsSupportedRegisterDefaultsVersion.

* [kernel] Add POSIX pthread_cond_timedwait export

SILENT HILL (#4) and Poppy Playtime (#3) crash on boot due to
missing POSIX pthread_cond_timedwait (NID 27bAgiJmOh0).

The Sony wrapper scePthreadCondTimedwait (NID BmMjYxmew1w) was
already implemented, but the raw POSIX symbol was not exported.
Added [SysAbiExport] for pthread_cond_timedwait delegating to
existing PthreadCondWaitCore with timed: true.

* [memory] Fix FlushInstructionCache null process handle

PhysicalVirtualMemory.cs called FlushInstructionCache with null as the
process handle in two places (SetProtection and TryWriteExclusive).
On Windows, a null handle does not reliably resolve to the current
process — the correct call is GetCurrentProcess() (pseudo-handle -1).

Also corrected the P/Invoke signature:
- Changed return type from void to bool with [return: MarshalAs(Bool)]
- Added SetLastError = true
- Added GetCurrentProcess() P/Invoke import

This matches the pattern already used in DirectExecutionBackend.cs
which correctly passes GetCurrentProcess() to all FlushInstructionCache
calls.

* [hle] Distinguish NOT_FOUND from NOT_IMPLEMENTED and log duplicate NIDs

Three diagnostic improvements to the HLE dispatch path:

1. ModuleManager.RegisterFromAssembly — duplicate NID registration was
   silently skipped (dispatchTable first-wins, exportTable last-wins,
   causing metadata divergence). Now logs a warning with the NID and
   export name so conflicts are visible.

2. ModuleManager.TryDispatch — generation mismatch returned
   ORBIS_GEN2_ERROR_NOT_FOUND, conflating 'function does not exist'
   with 'function exists but not for this generation'. Now returns
   ORBIS_GEN2_ERROR_NOT_IMPLEMENTED for generation mismatch, matching
   the existing convention in CpuDispatcher. Also adds debug logging
   for both NOT_FOUND and NOT_IMPLEMENTED paths.

3. DirectExecutionBackend.Imports.cs — the import dispatch else-branch
   (the actual hot path that bypasses ModuleManager.TyDispatch via
   cached export) had the same conflation. Split into:
   - else if (export exists but generation mismatch) → NOT_IMPLEMENTED
   - else (no export at all) → NOT_FOUND
   This makes runtime diagnostics correctly distinguish missing exports
   from generation-unsupported exports.

* [cpu] Check VirtualProtect return values in all stub creation paths

9 VirtualProtect calls in DirectExecutionBackend.cs had unchecked
return values. If VirtualProtect silently fails, memory protection
remains incorrect — stubs allocated with PAGE_EXECUTE_READWRITE (0x40)
never get downgraded to PAGE_EXECUTE_READ (0x20), or guest thread
entry stubs never get upgraded to writable. This causes access
violations on next execution or silent data corruption.

Fixed all 9 sites with proper error handling:
- 6 stub creation methods (return 0 on failure + log error)
- 2 guest thread entry methods (set reason + return Exception)
- 1 guest entry method (set LastError + return MEMORY_FAULT)

Stub creation sites fixed:
- CreateImportDispatchStub (line ~1683)
- EnsureTlsHandler (void, log + return)
- CreateUnresolvedReturnStub (return 0)
- CreateGuestReturnStub (return 0)
- CreateExceptionHandlerTrampoline (return 0)
- CreateTlsStoreHelperStub (return 0)

Guest thread entry sites fixed:
- StartGuestThreadNativeCall (return Exception)
- StartGuestContinuationNativeCall (return Exception)
- RunGuestEntryPoint (return MEMORY_FAULT)

* [kernel] Remove unused duplicate _nextFileDescriptor field

KernelExports.cs declared _nextFileDescriptor but never used it.
The actual field used for file descriptor allocation lives in
KernelMemoryCompatExports.cs (lines 1314, 1337). This was a dead
duplicate causing CS0414 warning.

Build is now 0 errors, 0 warnings.

---------

Co-authored-by: Hermes Atlas <hermesatlas@example.com>

src/SharpEmu.Libs/Agc/AgcExports.cs

@@ -58,6 +58,8 @@ public static class AgcExports
     private const uint SpiShaderPgmHiEs = 0xC9;
     private const uint SpiShaderPgmLoLs = 0x148;
     private const uint SpiShaderPgmHiLs = 0x149;
+    private const uint SpiShaderPgmLoGs = 0x8A;
+    private const uint SpiShaderPgmHiGs = 0x8B;
     private const uint SpiPsInputEna = 0x1B3;
     private const uint SpiPsInputAddr = 0x1B4;
     private const uint ComputePgmLo = 0x20C;
@@ -115,6 +117,7 @@ public static class AgcExports
     private const uint RegisterDefaultsVersion7 = 7;
     private const uint RegisterDefaultsVersion8 = 8;
     private const uint RegisterDefaultsVersion10 = 10;
+    private const uint RegisterDefaultsVersion13 = 13;
     private const int RegisterDefaultsSize = 0x40;
     private const int RegisterDefaultBlockSize = 16 * 8;
 
@@ -5081,6 +5084,7 @@ public static class AgcExports
             0 => ComputePgmLo,
             1 => SpiShaderPgmLoPs,
             2 or 6 => SpiShaderPgmLoEs,
+            4 => SpiShaderPgmLoGs,
             7 => SpiShaderPgmLoLs,
             _ => 0u,
         };
@@ -5089,6 +5093,7 @@ public static class AgcExports
             0 => ComputePgmHi,
             1 => SpiShaderPgmHiPs,
             2 or 6 => SpiShaderPgmHiEs,
+            4 => SpiShaderPgmHiGs,
             7 => SpiShaderPgmHiLs,
             _ => 0u,
         };
@@ -5105,7 +5110,7 @@ public static class AgcExports
     }
 
     private static bool IsEsGeometryShaderType(byte shaderType) =>
-        shaderType is 2 or 6;
+        shaderType is 2 or 4 or 6;
 
     private static int SetIndirectPatchAddress(CpuContext ctx, string registerSpace)
     {
@@ -5252,7 +5257,8 @@ public static class AgcExports
         return version is
             RegisterDefaultsVersion7 or
             RegisterDefaultsVersion8 or
-            RegisterDefaultsVersion10;
+            RegisterDefaultsVersion10 or
+            RegisterDefaultsVersion13;
     }
 
     private static bool TryGetRegisterDefaultsAllocation(

src/SharpEmu.Libs/Kernel/KernelExports.cs

@@ -8,7 +8,6 @@ namespace SharpEmu.Libs.Kernel;
 
 public static class KernelExports
 {
-    private static int _nextFileDescriptor = 2;
     private static readonly object _cxaGate = new();
     private static readonly List<CxaDestructorEntry> _cxaDestructors = new();
     private static readonly object _coredumpGate = new();

src/SharpEmu.Libs/Kernel/KernelPthreadCompatExports.cs

@@ -329,6 +329,12 @@ public static class KernelPthreadCompatExports
         Target = Generation.Gen4 | Generation.Gen5,
         LibraryName = "libKernel")]
     public static int PosixPthreadCondSignal(CpuContext ctx) => PthreadCondSignalCore(ctx, ctx[CpuRegister.Rdi], broadcast: false);
+    [SysAbiExport(
+        Nid = "27bAgiJmOh0",
+        ExportName = "pthread_cond_timedwait",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libKernel")]
+    public static int PosixPthreadCondTimedwait(CpuContext ctx) => PthreadCondWaitCore(ctx, ctx[CpuRegister.Rdi], ctx[CpuRegister.Rsi], timed: true, timeoutUsec: unchecked((uint)ctx[CpuRegister.Rdx]));
 
     [SysAbiExport(
         Nid = "m5-2bsNfv7s",