fix(extraction): a function in an initializer is referenced once, by what the initializer declares (#2743)

PRs #693 and #1802 walk a declaration's initializer under the symbol it declares,
so `const routes = { home }` references `home` from `routes`. The
dispatcher's declaration-wide function-as-value scan then took the same
values again for the enclosing file (or class). Flush-time dedup keys on
the source, so both stayed: a second reference to the same function from
the same spot.

Each initializer walk now records what it walked, and the scan skips it.
PR #2738 added that mechanism for component wrappers, and C#, Scala and Dart
already had their own. The newly covered paths:
- TS/JS module-level constants and variables, owned object literals
  included (#2300), and TS/JS class properties;
- Python assignments, Go var/const specs, Rust const/static items;
- Java fields, and Kotlin properties (walkInitializer takes the property's
  id, so their walk is unchanged).
Mirrored in the kernel: tsjs, python, go, rustlang, java and kotlin.

References no initializer walk takes are unchanged: a module-level call
argument `register(fn)`, C-family tables, Rust's `static CB: fn() = handler`
(the declaration's own value, which the scan still reads).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

codegraph-kernel/src/go.rs

@@ -428,8 +428,10 @@ impl<'t> Walker<'t> {
         } else if matches!(kind, "var_declaration" | "short_var_declaration" | "const_declaration")
             && !self.inside_class_like()
         {
-            self.extract_variable(node);
-            self.scan_fn_ref_subtree(node, 0);
+            // The initializers extract_variable walked under their specs'
+            // symbols took their own candidates; the scan covers the rest.
+            let walked = self.extract_variable(node);
+            self.scan_fn_ref_subtree(node, 0, &walked);
             skip_children = true;
         } else if kind == "import_declaration" {
             self.extract_import(node);
@@ -678,7 +680,10 @@ impl<'t> Walker<'t> {
     }
 
     /// extractVariable's Go branch: var/const specs + short_var_declaration.
-    fn extract_variable(&mut self, node: Node<'t>) {
+    /// Returns the initializers it walked under their specs' symbols, for the
+    /// declaration scan to skip.
+    fn extract_variable(&mut self, node: Node<'t>) -> Vec<usize> {
+        let mut walked = Vec::new();
         let docstring = self.docstring_of(node);
         let is_const_decl = node.kind() == "const_declaration";
 
@@ -726,6 +731,7 @@ impl<'t> Walker<'t> {
                     self.stack.push(Scope { row, kind: "variable", name });
                     self.visit_function_body(value_field);
                     self.stack.pop();
+                    walked.push(value_field.id());
                 } else {
                     self.visit_function_body(value_field);
                 }
@@ -756,6 +762,7 @@ impl<'t> Walker<'t> {
                 }
             }
         }
+        walked
     }
 
     /// extractImport's Go branch: one import node + ref per import_spec.
@@ -1241,11 +1248,15 @@ impl<'t> Walker<'t> {
         }
     }
 
-    fn scan_fn_ref_subtree(&mut self, node: Node<'t>, depth: u32) {
+    fn scan_fn_ref_subtree(&mut self, node: Node<'t>, depth: u32, walked: &[usize]) {
         stack_guard!();
         if depth > 12 {
             return;
         }
+        // Subtrees the body walker has already been through.
+        if walked.contains(&node.id()) {
+            return;
+        }
         if depth > 0
             && matches!(
                 node.kind(),
@@ -1258,7 +1269,7 @@ impl<'t> Walker<'t> {
         self.maybe_capture_fn_refs(node);
         for i in 0..node.named_child_count() {
             if let Some(c) = node.named_child(i) {
-                self.scan_fn_ref_subtree(c, depth + 1);
+                self.scan_fn_ref_subtree(c, depth + 1, walked);
             }
         }
     }