[Kernel] Implement clock_getres and the POSIX pthread_once alias

clock_getres (smIj7eqzZE8) was missing entirely. It reports 100ns, which
is the resolution clock_gettime here actually delivers via
DateTimeOffset.UtcNow, rather than claiming the 1ns a caller might
otherwise rely on. A null res pointer is accepted per POSIX.

pthread_once (Z4QosVuAsA0) needed no new logic: libKernel exports the
same routine under two NIDs and only scePthreadOnce (14bOACANTBo) was
registered. Shipped middleware links the plain name.

Both are imported by DOOM + DOOM II (PPSA21444): clock_getres blocked
party.prx from initialising, and pthread_once is used by libcohtml,
libPlayFabMultiplayer, party.prx and the eboot.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/SharpEmu.Libs/Kernel/KernelMemoryCompatExports.cs

@@ -2327,6 +2327,37 @@ public static partial class KernelMemoryCompatExports
         return (int)OrbisGen2Result.ORBIS_GEN2_OK;
     }
 
+    [SysAbiExport(
+        Nid = "smIj7eqzZE8",
+        ExportName = "clock_getres",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libKernel")]
+    public static int ClockGetres(CpuContext ctx)
+    {
+        var timespecAddress = ctx[CpuRegister.Rsi];
+
+        // POSIX allows a null resolution pointer: the call then only validates
+        // the clock id, which every id a title passes here does.
+        if (timespecAddress == 0)
+        {
+            ctx[CpuRegister.Rax] = 0;
+            return (int)OrbisGen2Result.ORBIS_GEN2_OK;
+        }
+
+        // clock_gettime above is backed by DateTimeOffset.UtcNow, whose tick is
+        // 100 ns, so that is the honest resolution to report rather than the 1 ns
+        // a caller might otherwise assume it can rely on.
+        const ulong ResolutionNanoseconds = 100;
+        if (!ctx.TryWriteUInt64(timespecAddress, 0) ||
+            !ctx.TryWriteUInt64(timespecAddress + sizeof(long), ResolutionNanoseconds))
+        {
+            return (int)OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT;
+        }
+
+        ctx[CpuRegister.Rax] = 0;
+        return (int)OrbisGen2Result.ORBIS_GEN2_OK;
+    }
+
     [SysAbiExport(
         Nid = "vNe1w4diLCs",
         ExportName = "__tls_get_addr",

src/SharpEmu.Libs/Kernel/KernelPthreadCompatExports.cs

@@ -578,6 +578,19 @@ public static class KernelPthreadCompatExports
         return SetReturn(ctx, OrbisGen2Result.ORBIS_GEN2_OK);
     }
 
+    /// <summary>
+    /// The POSIX-named alias of <see cref="PthreadOnce"/>. libKernel exports the
+    /// same routine under two NIDs, and shipped middleware links the plain name:
+    /// DOOM's libcohtml, PlayFab and party modules all import this one rather
+    /// than scePthreadOnce.
+    /// </summary>
+    [SysAbiExport(
+        Nid = "Z4QosVuAsA0",
+        ExportName = "pthread_once",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libKernel")]
+    public static int PthreadOncePOSIX(CpuContext ctx) => PthreadOnce(ctx);
+
     private static int PthreadMutexInitCore(CpuContext ctx, ulong mutexAddress, ulong attrAddress)
     {
         if (mutexAddress == 0)