fix: strip MSVC elaborated type specifiers from extracted type names

MSVC's __FUNCSIG__ prepends 'struct ' or 'class ' to type names when
there is no explicit scope qualifier (e.g. anonymous-namespace types
may appear as 'struct child_table_cascade' rather than
'`anonymous-namespace'::child_table_cascade').

When rfind("::") returns npos (no scope to strip), the full string
including 'struct '/'class ' was used as the table/column name,
producing e.g. CREATE TABLE struct child_table_cascade.

Fix: strip the elaborated type keyword prefix immediately after
substring extraction, before the scope-stripping and _tag-suffix
steps. Applied to both tag_to_column_name (column_field.hpp) and
extract_type_name (schema_generator.hpp). GCC/Clang are unaffected
since their __PRETTY_FUNCTION__ output never includes these keywords.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Pierre-Luc Gagné

lib/include/ds_mysql/column_field.hpp

@@ -78,6 +78,12 @@ consteval std::string_view tag_to_column_name() noexcept {
         return {};
     }
     auto name = sig.substr(start, end - start);
+    // MSVC prepends 'struct ' or 'class ' to type names; strip before scope/suffix processing.
+    if (name.starts_with("struct ")) {
+        name = name.substr(7);
+    } else if (name.starts_with("class ")) {
+        name = name.substr(6);
+    }
     auto const scope = name.rfind("::");
     if (scope != std::string_view::npos && scope + 2 < name.size()) {
         name = name.substr(scope + 2);

lib/include/ds_mysql/schema_generator.hpp

@@ -218,6 +218,13 @@ consteval std::string_view extract_type_name() {
 
     auto name = signature.substr(start, end - start);
 
+    // MSVC prepends 'struct ' or 'class ' to type names; strip before scope processing.
+    if (name.starts_with("struct ")) {
+        name = name.substr(7);
+    } else if (name.starts_with("class ")) {
+        name = name.substr(6);
+    }
+
     // Remove namespace qualifiers (keep only the final name)
     auto const scope_pos = name.rfind("::");
     if (scope_pos != std::string_view::npos && scope_pos + 2 < name.size()) {