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, 3 insertions, 1 deletions

diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index f82bf24c1..18c54587a 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -2297,7 +2297,9 @@ struct SPIRVEmitContext : public SourceEmitterBase, public SPIRVEmitSharedContex
                 auto moduleInst = inst->getModule()->getModuleInst();
                 if (!m_defaultDebugSource)
                     m_defaultDebugSource = debugSource;
-                if (!m_mapIRInstToSpvDebugInst.containsKey(moduleInst))
+                // Only create DebugCompilationUnit for non-included files
+                auto isIncludedFile = as<IRBoolLit>(debugSource->getIsIncludedFile())->getValue();
+                if (!m_mapIRInstToSpvDebugInst.containsKey(moduleInst) && !isIncludedFile)
                 {
                     IRBuilder builder(inst);
                     builder.setInsertBefore(inst);