feat: PDB import via RawPDB, no msdia140.dll dependency

Replace DIA SDK COM-based PDB importer with RawPDB (MolecularMatters)
which reads PDB files directly via memory-mapped I/O. Adds File menu
"Import PDB..." dialog with type filtering, selection, and progress.

- Vendor raw_pdb into third_party/
- Two-phase API: enumeratePdbTypes() + importPdbSelected()
- Full recursive import of structs/unions/arrays/pointers/bitfields
- PDB import dialog with name filter, select-all, type count
- Benchmark: 1654 types from ntkrnlmp.pdb in 16ms
- Reorganize import/export files into src/imports/

third_party/raw_pdb/src/PDB_TPIStream.h

@@ -0,0 +1,85 @@
+#pragma once
+
+#include "Foundation/PDB_Macros.h"
+#include "Foundation/PDB_ArrayView.h"
+#include "PDB_ErrorCodes.h"
+#include "PDB_TPITypes.h"
+#include "PDB_DirectMSFStream.h"
+#include "PDB_Util.h"
+
+// PDB TPI stream
+// https://llvm.org/docs/PDB/TpiStream.html
+namespace PDB
+{
+	class RawFile;
+
+
+	class PDB_NO_DISCARD TPIStream
+	{
+	public:
+		TPIStream(void) PDB_NO_EXCEPT;
+		TPIStream(TPIStream&& other) PDB_NO_EXCEPT;
+		TPIStream& operator=(TPIStream&& other) PDB_NO_EXCEPT;
+
+		explicit TPIStream(const RawFile& file) PDB_NO_EXCEPT;
+
+		PDB_NO_DISCARD inline const DirectMSFStream& GetDirectMSFStream(void) const PDB_NO_EXCEPT
+		{
+			return m_stream;
+		}
+
+		// Returns the index of the first type, which is not necessarily zero.
+		PDB_NO_DISCARD inline uint32_t GetFirstTypeIndex(void) const PDB_NO_EXCEPT
+		{
+			return m_header.typeIndexBegin;
+		}
+
+		// Returns the index of the last type.
+		PDB_NO_DISCARD inline uint32_t GetLastTypeIndex(void) const PDB_NO_EXCEPT
+		{
+			return m_header.typeIndexEnd;
+		}
+
+		// Returns the number of type records.
+		PDB_NO_DISCARD inline size_t GetTypeRecordCount(void) const PDB_NO_EXCEPT
+		{
+			return m_recordCount;
+		}
+
+		CodeView::TPI::RecordHeader ReadTypeRecordHeader(size_t offset) const PDB_NO_EXCEPT
+		{
+			const CodeView::TPI::RecordHeader header = m_stream.ReadAtOffset<CodeView::TPI::RecordHeader>(offset);
+			return header;
+		}
+
+		template <typename F>
+		void ForEachTypeRecordHeaderAndOffset(F&& functor) const PDB_NO_EXCEPT
+		{
+			// ignore the stream's header
+			size_t offset = sizeof(TPI::StreamHeader);
+
+			while (offset < m_stream.GetSize())
+			{
+				const CodeView::TPI::RecordHeader header = ReadTypeRecordHeader(offset);
+
+				functor(header, offset);
+
+				// position the stream offset at the next record
+				offset += sizeof(CodeView::TPI::RecordHeader) + header.size - sizeof(uint16_t);
+			}
+		}
+
+	private:
+		DirectMSFStream m_stream;
+		TPI::StreamHeader m_header;
+		size_t m_recordCount;
+
+		PDB_DISABLE_COPY(TPIStream);
+	};
+
+	// Returns whether the given raw file provides a valid TPI stream.
+	PDB_NO_DISCARD ErrorCode HasValidTPIStream(const RawFile& file) PDB_NO_EXCEPT;
+
+	// Creates the TPI stream from a raw file.
+	PDB_NO_DISCARD TPIStream CreateTPIStream(const RawFile& file) PDB_NO_EXCEPT;
+}