Fix DebugCompilationUnit to reference main shader file instead of header files (#7957)

This PR implements the requested fix for issue #7923 where
DebugCompilationUnit incorrectly referenced header files instead of the
main shader file.

## Summary

- Modified IRDebugSource to include isIncludedFile flag as third operand
- Updated emitDebugSource function to accept and pass the included file
flag
- Updated call sites to use source->isIncludedFile() from SourceFile
class
- Modified SPIR-V emission to only create DebugCompilationUnit for
non-included files

## Test Results

The fix has been verified with the provided reproducer code. The SPIR-V
output now correctly shows DebugCompilationUnit referencing the main
shader file instead of header files.

Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Lujin Wang <lujinwangnv@users.noreply.github.com>
Co-authored-by: Claude Code <claude@anthropic.com>
Co-authored-by: slangbot <ellieh+slangbot@nvidia.com>
Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/tests/spirv/shader-utils.slang b/tests/spirv/shader-utils.slang
new file mode 100644
index 000000000..967991ad3
--- /dev/null
+++ b/tests/spirv/shader-utils.slang
@@ -0,0 +1,18 @@
+#ifndef SHADER_UTILS_SLANG
+#define SHADER_UTILS_SLANG
+
+// Helper function to calculate distance from center
+float calculateDistanceFromCenter(float2 uv)
+{
+    float2 center = float2(0.5, 0.5);
+    return length(uv - center);
+}
+
+// Additional utility function - simple smoothstep fade
+float createRadialFade(float2 uv, float radius)
+{
+    float dist = calculateDistanceFromCenter(uv);
+    return smoothstep(radius, 0.0, dist);
+}
+
+#endif // SHADER_UTILS_SLANG
\ No newline at end of file