Shader: test a wave mask consumed as a per-lane predicate at the lane bit (#465)

* Shader: read a wave mask consumed as a per-lane predicate at the lane bit

A VCC/EXEC wave mask consumed as a per-lane predicate (the VCndmask
condition, a VCC/EXEC branch, or the derived _vcc/_exec bool) was tested in
single-lane emulation with a whole-word non-zero test (IsNotZero64) instead
of the current lane's bit. That is correct for comparison results (only the
lane's own bit is ever set) but wrong for bitwise-complement wave-mask idioms
(S_NOT / S_ORN2 / S_ANDN2 / S_NAND / S_NOR), which set the unused upper 63
bits: a whole-word test then reports the lane active even when its bit is
clear.

Unity's PostProcessing NaN killer does exactly this: per channel it computes
isNaN = NLT AND NGT AND NEQ (against 0), then combines the channels as
anyNaN OR NOT(v3-is-finite) via S_ORN2_B64. The complement set the upper mask
bits, so every valid pixel read as NaN and was replaced with 0, zeroing the
whole HDR scene before Bloom/Uber/tonemap. The 3D scene therefore rendered
black behind the menu while the UI survived. Extract the current lane's bit in
both single-lane and subgroup modes so IsWaveMaskActive matches the hardware.

Fixes Superliminal (PPSA06084) black 3D scene: the storage room now renders
behind the menu with natural exposure and no forced values.

(cherry picked from commit 7af6f4b6f314fe302619c0d44f4db00971c5bf24)

* test: wave-mask predicate is tested at the current lane bit

Regression test for the wave-mask lane-bit fix. Compiles a shader that
writes VCC at run time (V_CMP_EQ_F32) and asserts the emitted SPIR-V tests
the wave mask at the current lane's bit (mask & lane_bit) rather than with a
whole-word non-zero test. Fails against the previous IsNotZero64(mask) path,
which zeroed complement wave-mask idioms (S_ORN2/S_NOT, e.g. Unity's NaN
killer) across every lane.

src/SharpEmu.ShaderCompiler.Vulkan/Gen5SpirvTranslator.cs

@@ -5290,10 +5290,20 @@ public static partial class Gen5SpirvTranslator
                 UInt(0x108));
         }
 
+        // A wave-mask SGPR (VCC/EXEC) consumed as a per-lane predicate — the
+        // condition of VCndmask, a VCC/EXEC branch, or the derived _vcc/_exec
+        // bool — must be tested at the CURRENT lane's bit, exactly as the
+        // hardware does, not as "the 64-bit value is non-zero". The two coincide
+        // for comparison results (only the lane's own bit is ever set), so the
+        // single-lane path historically used a cheaper whole-word non-zero test.
+        // But bitwise-complement wave-mask idioms (S_NOT/S_ORN2/S_ANDN2/S_NAND/
+        // S_NOR on a 64-bit mask) set the unused upper 63 bits; a whole-word test
+        // then reports "lane active" even when this lane's bit is clear. Unity's
+        // PostProcessing NaN killer does exactly this (`anyNaN | ~allFinite`),
+        // which made every valid pixel read as NaN and get replaced with 0 —
+        // zeroing the whole scene before tonemap. Extract the lane bit always.
         private uint IsWaveMaskActive(uint mask) =>
-            _subgroupInvocationIdInput == 0
-                ? IsNotZero64(mask)
-                : IsCurrentLaneSet(mask);
+            IsCurrentLaneSet(mask);
 
         private uint IsCurrentLaneSet(uint mask) =>
             IsNotZero64(