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/symbolstore.h

@@ -14,6 +14,7 @@ struct PdbSymbolSet {
     QString pdbPath;
     QString moduleName;          // canonical lowercase name (e.g. "ntoskrnl")
     QHash<QString, uint32_t> nameToRva;
+    QHash<QString, uint32_t> nameToTypeIndex; // symbol name → TPI typeIndex (0 = no type info)
     QVector<QPair<uint32_t, QString>> rvaToName;  // sorted by RVA for binary search
 
     void sortRvaIndex() {
@@ -35,6 +36,15 @@ public:
     int addModule(const QString& moduleName, const QString& pdbPath,
                   const QVector<QPair<QString, uint32_t>>& symbols);
 
+    // Store symbol→typeIndex mapping for a previously-added module.
+    // Called after addModule with the typeIndex data from PdbSymbol records.
+    void addModuleTypeIndices(const QString& moduleName,
+                              const QHash<QString, uint32_t>& nameToTypeIndex);
+
+    // Look up the TPI typeIndex for a qualified symbol (e.g. "ntdll!g_pShimEngineModule").
+    // Returns 0 if not found or no type info available.
+    uint32_t typeIndexForSymbol(const QString& qualifiedSymbol) const;
+
     // Unload symbols for a module.
     void unloadModule(const QString& moduleName);