feat: extract typeIndex from PDB symbols and add symbols.importType MCP tool

extractPdbSymbols() was reading S_GDATA32/S_GTHREAD32 records which
contain a typeIndex field linking the symbol to its type definition in
the TPI stream, but this field was discarded — only name + RVA were
kept. This meant loading symbols gave you address resolution but no
way to automatically import the type associated with a global variable.

Changes:
- PdbSymbol now carries typeIndex (0 = no type info / public symbol)
- extractPdbSymbols() captures typeIndex from all global data symbols
- PdbSymbolSet stores nameToTypeIndex mapping alongside nameToRva
- New importTypeForSymbol() follows LF_POINTER/LF_MODIFIER chains to
  find the underlying UDT/enum and imports it with full recursive children
- New symbols.importType MCP tool: given "ntdll!g_pShimEngineModule",
  resolves its typeIndex, imports the type definition from the PDB, and
  merges it into the active project
- loadPdbIntoStore() helper consolidates the extract+store pattern with
  type index support

src/imports/import_pdb.h

@@ -10,6 +10,7 @@ namespace rcx {
 struct PdbSymbol {
     QString name;
     uint32_t rva;
+    uint32_t typeIndex = 0;  // TPI type index (0 = unknown / public symbol)
 };
 
 struct PdbSymbolResult {
@@ -51,4 +52,12 @@ NodeTree importPdb(const QString& pdbPath,
                    const QString& structFilter = {},
                    QString* errorMsg = nullptr);
 
+// Import the type associated with a global symbol's typeIndex.
+// Opens the PDB, resolves the typeIndex to a UDT/enum, and returns the imported tree.
+// Returns empty tree if the symbol has no associated type or the type is a simple primitive.
+NodeTree importTypeForSymbol(const QString& pdbPath,
+                             uint32_t typeIndex,
+                             QString* typeName = nullptr,
+                             QString* errorMsg = nullptr);
+
 } // namespace rcx