feat(native): port Objective-C extractor to Rust

Mirrors `src/extractors/objc.ts` in `crates/codegraph-core/src/extractors/objc.rs`.
Adds the `tree-sitter-objc` dependency, wires `LanguageKind::ObjC` (`.m`) in
the Rust `parser_registry` and `file_collector`, adds `.m` to
`NATIVE_SUPPORTED_EXTENSIONS` on the JS side, and registers
`OBJC_AST_TYPES` / `OBJC_AST_CONFIG` so the native and WASM engines extract
identical `ast_nodes` for Objective-C source.

Handles class interfaces / implementations (with `: Superclass`), protocols,
instance and class method declarations/definitions with multi-part selectors
assembled from leading identifiers and `method_parameter` children, C-level
function declarations/definitions, `#import`/`@import` imports, and message
expression call extraction.

Author: carlos-alm

Cargo.lock

@@ -35,6 +35,7 @@ tree-sitter-dart = "0.0.4"
 tree-sitter-zig = "1"
 tree-sitter-haskell = "0.23"
 tree-sitter-ocaml = "0.24"
+tree-sitter-objc = "3"
 rayon = "1"
 ignore = "0.4"
 globset = "0.4"

crates/codegraph-core/Cargo.toml

@@ -360,6 +360,19 @@ pub const OCAML_AST_CONFIG: LangAstConfig = LangAstConfig {
     string_prefixes: &[],
 };
 
+/// Objective-C string literals use the `@"..."` prefix. The shared
+/// `build_string_node` strips a leading `@` before applying prefixes, so we
+/// don't need to list it explicitly here.
+pub const OBJC_AST_CONFIG: LangAstConfig = LangAstConfig {
+    new_types: &[],
+    throw_types: &["throw_statement"],
+    await_types: &[],
+    string_types: &["string_literal"],
+    regex_types: &[],
+    quote_chars: &['"'],
+    string_prefixes: &[],
+};
+
 // ── Generic AST node walker ──────────────────────────────────────────────────
 
 /// Node types that represent identifiers across languages.

crates/codegraph-core/src/extractors/helpers.rs

@@ -12,6 +12,7 @@ pub mod java;
 pub mod javascript;
 pub mod kotlin;
 pub mod lua;
+pub mod objc;
 pub mod ocaml;
 pub mod php;
 pub mod python;
@@ -126,5 +127,8 @@ pub fn extract_symbols_with_opts(
         LanguageKind::Ocaml | LanguageKind::OcamlInterface => {
             ocaml::OcamlExtractor.extract_with_opts(tree, source, file_path, include_ast_nodes)
         }
+        LanguageKind::ObjC => {
+            objc::ObjCExtractor.extract_with_opts(tree, source, file_path, include_ast_nodes)
+        }
     }
 }