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/python.ts

@@ -0,0 +1,53 @@
+import { getNodeText, getChildByField } from '../tree-sitter-helpers';
+import type { LanguageExtractor } from '../tree-sitter-types';
+
+export const pythonExtractor: LanguageExtractor = {
+  functionTypes: ['function_definition'],
+  classTypes: ['class_definition'],
+  methodTypes: ['function_definition'], // Methods are functions inside classes
+  interfaceTypes: [],
+  structTypes: [],
+  enumTypes: [],
+  typeAliasTypes: [],
+  importTypes: ['import_statement', 'import_from_statement'],
+  callTypes: ['call'],
+  variableTypes: ['assignment'], // Python uses assignment for variable declarations
+  nameField: 'name',
+  bodyField: 'body',
+  paramsField: 'parameters',
+  returnField: 'return_type',
+  getSignature: (node, source) => {
+    const params = getChildByField(node, 'parameters');
+    const returnType = getChildByField(node, 'return_type');
+    if (!params) return undefined;
+    let sig = getNodeText(params, source);
+    if (returnType) {
+      sig += ' -> ' + getNodeText(returnType, source);
+    }
+    return sig;
+  },
+  isAsync: (node) => {
+    const prev = node.previousSibling;
+    return prev?.type === 'async';
+  },
+  isStatic: (node) => {
+    // Check for @staticmethod decorator
+    const prev = node.previousNamedSibling;
+    if (prev?.type === 'decorator') {
+      const text = prev.text;
+      return text.includes('staticmethod');
+    }
+    return false;
+  },
+  extractImport: (node, source) => {
+    const importText = source.substring(node.startIndex, node.endIndex).trim();
+    if (node.type === 'import_from_statement') {
+      const moduleNode = node.childForFieldName('module_name');
+      if (moduleNode) {
+        return { moduleName: source.substring(moduleNode.startIndex, moduleNode.endIndex), signature: importText };
+      }
+    }
+    // import_statement creates multiple imports - return null for core fallback
+    return null;
+  },
+};