[Font] Implement sceFontGetVerticalLayout (#492)

Add sceFontGetVerticalLayout (NID: 3BrWWFU+4ts) to the Font module,
completing the vertical-text counterpart to the existing
GetHorizontalLayout. The SceFontVerticalLayout structure is three
floats (baseline, lineAdvance, decorationExtent) interpreted for
vertical writing such as CJK text rendered top-to-bottom.

- Write baseline=8.0f, lineAdvance=16.0f, decorationExtent=0.0f
- Validate output pointer and return INVALID_ARGUMENT on null
- Return MEMORY_FAULT when guest writes fail

Tests:
- GetVerticalLayout_WritesExactlyThreeFloats with sentinel guard
- GetVerticalLayout_NullBuffer_ReturnsInvalidArgument

NID sourced via: python scripts/aerolib_catalog.py lookup sceFontGetVerticalLayout

Co-authored-by: tru3 <tru3@tru3.com>

src/SharpEmu.Libs/Font/FontExports.cs

@@ -153,6 +153,37 @@ public static class FontExports
         return SetSuccess(ctx);
     }
 
+    [SysAbiExport(
+        Nid = "3BrWWFU+4ts",
+        ExportName = "sceFontGetVerticalLayout",
+        Target = Generation.Gen5,
+        LibraryName = "libSceFont")]
+    public static int GetVerticalLayout(CpuContext ctx)
+    {
+        var layoutAddress = ctx[CpuRegister.Rsi];
+        if (layoutAddress == 0)
+        {
+            return SetReturn(ctx, OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT);
+        }
+
+        // Baseline (horizontal offset), line advance, decoration extent.
+        // Mirrors the same three-float layout as GetHorizontalLayout, but
+        // interpreted for vertical writing (e.g. CJK text rendered top-to-bottom).
+        var values = new[] { 8.0f, 16.0f, 0.0f };
+        for (var index = 0; index < values.Length; index++)
+        {
+            if (!TryWriteUInt32(
+                    ctx,
+                    layoutAddress + (ulong)(index * sizeof(float)),
+                    BitConverter.SingleToUInt32Bits(values[index])))
+            {
+                return SetReturn(ctx, OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT);
+            }
+        }
+
+        return SetSuccess(ctx);
+    }
+
     [SysAbiExport(
         Nid = "cKYtVmeSTcw",
         ExportName = "sceFontOpenFontSet",

tests/SharpEmu.Libs.Tests/Font/FontExportsTests.cs

@@ -41,4 +41,32 @@ public sealed class FontExportsTests
         Assert.Equal(0.0f, BinaryPrimitives.ReadSingleLittleEndian(layout[8..]));
         Assert.Equal(Sentinel, BinaryPrimitives.ReadUInt32LittleEndian(layout[12..]));
     }
+
+    [Fact]
+    public void GetVerticalLayout_WritesExactlyThreeFloats()
+    {
+        const uint Sentinel = 0xDEADBEEF;
+        Span<byte> sentinelBytes = stackalloc byte[sizeof(uint)];
+        BinaryPrimitives.WriteUInt32LittleEndian(sentinelBytes, Sentinel);
+        Assert.True(_ctx.Memory.TryWrite(LayoutAddress + 12, sentinelBytes));
+
+        _ctx[CpuRegister.Rsi] = LayoutAddress;
+        Assert.Equal(0, FontExports.GetVerticalLayout(_ctx));
+
+        Span<byte> layout = stackalloc byte[16];
+        Assert.True(_ctx.Memory.TryRead(LayoutAddress, layout));
+        Assert.Equal(8.0f, BinaryPrimitives.ReadSingleLittleEndian(layout));
+        Assert.Equal(16.0f, BinaryPrimitives.ReadSingleLittleEndian(layout[4..]));
+        Assert.Equal(0.0f, BinaryPrimitives.ReadSingleLittleEndian(layout[8..]));
+        Assert.Equal(Sentinel, BinaryPrimitives.ReadUInt32LittleEndian(layout[12..]));
+    }
+
+    [Fact]
+    public void GetVerticalLayout_NullBuffer_ReturnsInvalidArgument()
+    {
+        _ctx[CpuRegister.Rsi] = 0;
+        Assert.Equal(
+            (int)OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT,
+            FontExports.GetVerticalLayout(_ctx));
+    }
 }