fix(extraction): skip bodiless C++ forward declarations (#1093) (#1095)

A `class Foo;` forward declaration parses as a bodiless class_specifier.
extractStruct (#831) and extractEnum already skip their bodiless forms,
but extractClass did not — so every forward decl across dozens of headers
minted a phantom bodiless `class` node that competed with, and could be
picked as the blast-radius representative over, the single real definition.

Add an opt-in `skipBodilessClass` extractor flag (set only on cppExtractor)
and skip a bodiless class node when it's set, mirroring the struct/enum
skip. The flag keeps this C/C++-scoped: languages where a bodiless class is
a complete definition (Kotlin `class Empty`, Scala `case object`/`trait`)
leave it unset and are unaffected. The body is now resolved once at the top
of extractClass and reused for the member walk.

Regression tests cover the collapse to a single definition, elaborated-type
references creating no phantom, and Kotlin/Scala staying indexed.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/extraction/tree-sitter-types.ts

@@ -163,6 +163,14 @@ export interface LanguageExtractor {
   extraClassNodeTypes?: string[];
   /** Whether methods can be top-level without enclosing class (Go: true) */
   methodsAreTopLevel?: boolean;
+  /**
+   * Skip a bodiless class node as a forward declaration / elaborated type,
+   * mirroring the bodiless-struct/enum skip. Set only for languages where a
+   * bodiless `class` specifier is NOT a complete definition — C/C++
+   * (`class Foo;` is a forward decl). Leave unset for languages where a
+   * bodiless class IS complete (Kotlin `class Empty`, Scala `case object`). (#1093)
+   */
+  skipBodilessClass?: boolean;
   /** NodeKind to use for interface-like declarations (Rust: 'trait'). Default: 'interface' */
   interfaceKind?: NodeKind;