fix(extraction): extract type refs from TS interface property and method signatures (#432)

Types that appeared only in TypeScript interface members — property
signatures like `value?: Partial<IPage>` and method signatures like
`fetchPage(arg: IPage): IOrderField` — were not being captured at
extraction time, so the resolver never built `references` edges for
them. `codegraph_impact`/`codegraph_callers` on the named type missed
every consumer that imported it solely to use it in an interface shape.

Add a `property_signature` / `method_signature` branch in `visitNode`:
when inside a class-like node (which covers interfaces) and the
language supports type annotations, call `extractTypeAnnotations` with
the parent (interface) node ID as the edge source. No property/method
node is created — only unresolved references that the resolver wires
the same way it wires field and parameter type references elsewhere.

src/extraction/tree-sitter.ts

@@ -387,6 +387,22 @@ export class TreeSitterExtractor {
     else if (nodeType === 'impl_item') {
       this.extractRustImplItem(node);
     }
+    // TypeScript interface members: property_signature (`foo: T`, `foo?: T`)
+    // and method_signature (`foo(arg: A): R`) both carry type annotations the
+    // interface walker would otherwise drop. Extract them as `references`
+    // edges from the interface so resolvers can wire callers/impact for
+    // types that only appear in interface members.
+    else if (
+      (nodeType === 'property_signature' || nodeType === 'method_signature') &&
+      this.isInsideClassLikeNode() &&
+      this.TYPE_ANNOTATION_LANGUAGES.has(this.language)
+    ) {
+      const parentId = this.nodeStack[this.nodeStack.length - 1];
+      if (parentId) {
+        this.extractTypeAnnotations(node, parentId);
+      }
+      // don't skipChildren — nested signatures still need traversal
+    }
 
     // Visit children (unless the extract method already visited them)
     if (!skipChildren) {