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.HLE/ModuleManager.cs

@@ -47,6 +47,7 @@ public sealed class ModuleManager : IModuleManager
                     var handler = CreateHandler(type, method, instances);
                     if (!_dispatchTable.TryAdd(exportInfo.Value.Nid, handler))
                     {
+                        Console.Error.WriteLine($"[HLE] Duplicate NID '{exportInfo.Value.Nid}' ({exportInfo.Value.ExportName}) — already registered, skipping.");
                         continue;
                     }
 
@@ -105,6 +106,7 @@ public sealed class ModuleManager : IModuleManager
 
         if (!_dispatchTable.TryGetValue(nid, out var function) || !_exportTable.TryGetValue(nid, out var export))
         {
+            Console.Error.WriteLine($"[HLE] NID '{nid}' not found in dispatch table.");
             context[CpuRegister.Rax] = unchecked((ulong)(int)OrbisGen2Result.ORBIS_GEN2_ERROR_NOT_FOUND);
             result = OrbisGen2Result.ORBIS_GEN2_ERROR_NOT_FOUND;
             return false;
@@ -112,11 +114,13 @@ public sealed class ModuleManager : IModuleManager
 
         if ((export.Target & context.TargetGeneration) == 0)
         {
-            context[CpuRegister.Rax] = unchecked((ulong)(int)OrbisGen2Result.ORBIS_GEN2_ERROR_NOT_FOUND);
-            result = OrbisGen2Result.ORBIS_GEN2_ERROR_NOT_FOUND;
+            Console.Error.WriteLine($"[HLE] NID '{nid}' ({export.Name}) found but not implemented for generation {context.TargetGeneration} (targets: {export.Target}).");
+            context[CpuRegister.Rax] = unchecked((ulong)(int)OrbisGen2Result.ORBIS_GEN2_ERROR_NOT_IMPLEMENTED);
+            result = OrbisGen2Result.ORBIS_GEN2_ERROR_NOT_IMPLEMENTED;
             return false;
         }
 
+
         context.ClearRaxWriteFlag();
         int ret = ((SysAbiFunction)function).Invoke(context);