refactor: Extract per-language configs and standalone extractors from tree-sitter.ts

Splits the monolithic tree-sitter.ts (3,358 lines) into modular files:
- 14 language config files under src/extraction/languages/
- 3 standalone extractors (Liquid, Svelte, DFM)
- Shared helpers and types modules to avoid circular imports

Also fixes a bug where Java's extractImport hook incorrectly set
handledRefs: true, preventing unresolved reference creation and
degrading codegraph_explore results for Java codebases.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/extraction/languages/index.ts

@@ -0,0 +1,44 @@
+/**
+ * Per-language extraction configurations.
+ *
+ * Each file exports a LanguageExtractor config object.
+ * This barrel builds the EXTRACTORS map consumed by TreeSitterExtractor.
+ */
+
+import { Language } from '../../types';
+import type { LanguageExtractor } from '../tree-sitter-types';
+
+import { typescriptExtractor } from './typescript';
+import { javascriptExtractor } from './javascript';
+import { pythonExtractor } from './python';
+import { goExtractor } from './go';
+import { rustExtractor } from './rust';
+import { javaExtractor } from './java';
+import { cExtractor, cppExtractor } from './c-cpp';
+import { csharpExtractor } from './csharp';
+import { phpExtractor } from './php';
+import { rubyExtractor } from './ruby';
+import { swiftExtractor } from './swift';
+import { kotlinExtractor } from './kotlin';
+import { dartExtractor } from './dart';
+import { pascalExtractor } from './pascal';
+
+export const EXTRACTORS: Partial<Record<Language, LanguageExtractor>> = {
+  typescript: typescriptExtractor,
+  tsx: typescriptExtractor,
+  javascript: javascriptExtractor,
+  jsx: javascriptExtractor,
+  python: pythonExtractor,
+  go: goExtractor,
+  rust: rustExtractor,
+  java: javaExtractor,
+  c: cExtractor,
+  cpp: cppExtractor,
+  csharp: csharpExtractor,
+  php: phpExtractor,
+  ruby: rubyExtractor,
+  swift: swiftExtractor,
+  kotlin: kotlinExtractor,
+  dart: dartExtractor,
+  pascal: pascalExtractor,
+};