feat(kernel): R2 — full TypeScript/JavaScript extraction port, byte-parity with the wasm path

Replaces the R1 seed .scm emitter with a bespoke Rust walker
(codegraph-kernel/src/tsjs/) that mirrors TreeSitterExtractor's TS/JS
paths function-for-function: declarations (incl. #808 field/property
classification), qualified names, docstrings (#780 wrapper climbs),
signatures, imports/re-exports + per-binding refs, calls with
receiver-qualified callees (#1230 literal-receiver skip), instantiations,
decorators, inheritance, type annotations (#381), type-alias members +
tuple contracts (#359/#634), React component recognition (#841
forwardRef/memo/styled), object-of-functions / zustand-through-middleware
/ RTK Query endpoints + generated hooks / vuex + pinia store shapes,
function-as-value capture with the flush gate (#756), and value-reference
edges with the shadow prune (#895/#897). The generic query emitter is
deleted — extraction parity needs logic .scm can't express; future
languages get walkers too (migration plan §4a).

Positions and JS string-slice semantics are emitted in UTF-16 code units
natively, so kernel output is byte-identical to web-tree-sitter's — no
column diff class exists.

Parity evidence (macOS): scripts/kernel-parity.mjs (full-object multiset
diff per file) — this repo 353/353 files, excalidraw 643/643 (10,650
nodes / 10,726 edges / 68,307 refs), plus torture fixtures checked into
__tests__/fixtures/kernel-parity/ and enforced in npm test by
kernel-tsjs-parity.test.ts. The strict compare caught one real decoder
bug the loose harness missed: refs must NOT carry denormalized
filePath/language at the extractFromSource seam (the store fills them).

Perf: extraction 2.6× single-thread on excalidraw (487ms vs 1,255ms,
identical outputs). Routing stays opt-in (CODEGRAPH_KERNEL_LANGS) until
the R3 equivalence gate (large repo, DB dump-diff, retrieval invariants,
agent A/B, Linux/Windows) passes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

__tests__/fixtures/kernel-parity/torture.js

@@ -0,0 +1,75 @@
+/**
+ * JS-grammar torture fixture (javascript variant: no type machinery, JS class
+ * fields use `field_definition` with a `property` field).
+ */
+import { EventEmitter } from 'node:events';
+const { promisify } = require('node:util');
+
+/** Legacy prototype-style helper. */
+function legacyHelper(a, b) {
+  return a + b;
+}
+
+const arrow = (x) => legacyHelper(x, 1);
+
+class Widget extends EventEmitter {
+  static registry = new Map();
+  #privateField = 1;
+  label = 'w';
+  onTick = () => {
+    this.render();
+  };
+  wrapped = debounce(function () {
+    expensive();
+  }, 50);
+
+  constructor(opts) {
+    super();
+    this.opts = opts;
+    register(this.onTick);
+  }
+
+  render() {
+    paint(this.label);
+  }
+
+  static create(opts) {
+    return new Widget(opts);
+  }
+}
+
+// AMD-style wrapper — anonymous, but inner functions must still surface.
+(function () {
+  function hiddenInner() {
+    return 7;
+  }
+  hiddenInner();
+})();
+
+module.exports.makeWidget = function makeWidget(opts) {
+  return Widget.create(opts);
+};
+
+// Vuex module shape (store-file signals: mutations + actions + getters).
+const mutations = {
+  SET_USER(state, user) {
+    state.user = user;
+  },
+};
+const actions = {
+  async loadUser({ commit }, id) {
+    const user = await fetchUser(id);
+    commit('SET_USER', user);
+  },
+};
+export default {
+  namespaced: true,
+  state: () => ({ user: null }),
+  mutations,
+  actions,
+  getters: {
+    userName(state) {
+      return state.user?.name;
+    },
+  },
+};