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/javascript.ts

@@ -0,0 +1,56 @@
+import { getNodeText, getChildByField } from '../tree-sitter-helpers';
+import type { LanguageExtractor } from '../tree-sitter-types';
+
+export const javascriptExtractor: LanguageExtractor = {
+  functionTypes: ['function_declaration', 'arrow_function', 'function_expression'],
+  classTypes: ['class_declaration'],
+  methodTypes: ['method_definition', 'field_definition'],
+  interfaceTypes: [],
+  structTypes: [],
+  enumTypes: [],
+  typeAliasTypes: [],
+  importTypes: ['import_statement'],
+  callTypes: ['call_expression'],
+  variableTypes: ['lexical_declaration', 'variable_declaration'],
+  nameField: 'name',
+  bodyField: 'body',
+  paramsField: 'parameters',
+  getSignature: (node, source) => {
+    const params = getChildByField(node, 'parameters');
+    return params ? getNodeText(params, source) : undefined;
+  },
+  isExported: (node, _source) => {
+    let current = node.parent;
+    while (current) {
+      if (current.type === 'export_statement') return true;
+      current = current.parent;
+    }
+    return false;
+  },
+  isAsync: (node) => {
+    for (let i = 0; i < node.childCount; i++) {
+      const child = node.child(i);
+      if (child?.type === 'async') return true;
+    }
+    return false;
+  },
+  isConst: (node) => {
+    if (node.type === 'lexical_declaration') {
+      for (let i = 0; i < node.childCount; i++) {
+        const child = node.child(i);
+        if (child?.type === 'const') return true;
+      }
+    }
+    return false;
+  },
+  extractImport: (node, source) => {
+    const sourceField = node.childForFieldName('source');
+    if (sourceField) {
+      const moduleName = source.substring(sourceField.startIndex, sourceField.endIndex).replace(/['"]/g, '');
+      if (moduleName) {
+        return { moduleName, signature: source.substring(node.startIndex, node.endIndex).trim() };
+      }
+    }
+    return null;
+  },
+};