feat(kernel): R3 — TS/JS equivalence gate passed, kernel default-on

Gate evidence (docs/design/rust-kernel-migration-plan.md §4b):

- Graph parity, byte-identical (stronger than the §5 ≤0.5% bar): full
  codegraph-init dump-diffs kernel-vs-wasm on express (13,712 rows),
  excalidraw (89,898), and vscode (2,378,238 rows) — identical bytes.
  Python control repo (flask) identical + timing unchanged. The parity
  harness is now ORDER-sensitive (emission order drives rowids, which
  drive resolution order) and dumps come from the new
  scripts/dump-graph.mjs (natural keys, no rowids/timestamps).

- The one real find, caught by the vscode tier: tree-sitter error
  RECOVERY is encoding-dependent — byte-identical grammar sources and
  the same core (0.25.10) recover erroring files differently under
  UTF-8 (native) vs UTF-16 (web-tree-sitter) parsing; proven by
  reproducing the wasm tree with a native UTF-16 parse. Policy: the
  kernel defers any file whose tree has_error() to the wasm extractor
  (silent 'defer:' signal, per file) — parity by construction on
  erroring files (incidence 0-0.42% across the gate repos), and the
  harness fails if deferrals exceed 10% so a broken kernel can't hide
  behind the fallback.

- Retrieval invariants: canonical excalidraw flow (mutateElement →
  renderStaticScene) connects end-to-end on the kernel-indexed graph;
  synthesized-edge families present. Agent A/B is vacuous under
  byte-identical DBs (same justification as #1320-#1322).

- Perf: vscode init 105.4s → 82.1s (1.28×) on an 11-core Mac;
  excalidraw on a 2-CPU/6GB Linux container (the CI-runner envelope)
  6.2-7.1s → 4.3-4.8s (~1.5×). Linux arm64 in-container build: all 22
  kernel tests green under CODEGRAPH_KERNEL_EXPECT=1. Windows VM leg
  deferred (VM stopped; prlctl start needs Parallels Pro) — benign: a
  missing .node falls back to wasm, and the release matrix builds and
  gates the win32 prebuilds.

- Full suite: 2,465 tests pass WITH default-on routing, so the entire
  extraction corpus now exercises the kernel for TS/JS wherever a
  .node is staged.

DEFAULT_ROUTED = {typescript, tsx, javascript, jsx}. Override:
CODEGRAPH_KERNEL_LANGS (replaces the set) / CODEGRAPH_KERNEL=0 (kill).
Changelog entry added under [Unreleased].

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

codegraph-kernel/src/tsjs/mod.rs

@@ -177,6 +177,19 @@ pub fn extract(file_path: &str, source: &str, language: &str) -> Result<EmitOut,
         .parse(source, None)
         .ok_or_else(|| "parser returned null tree".to_string())?;
 
+    // Files with parse ERRORS defer to the wasm extractor (the `defer:` prefix
+    // tells the TS side this is expected routing, not a malfunction). Reason:
+    // tree-sitter's error RECOVERY — same grammar, same core version — resolves
+    // differently under UTF-8 (native) vs UTF-16 (web-tree-sitter) parsing, so
+    // an erroring file's tree can differ between the paths (proven on vscode:
+    // `readonly import('x').T[]` recovered with the ERROR inside vs outside the
+    // type annotation). Erroring files are rare (0-0.42% across express/
+    // excalidraw/vscode) and per-file wasm fallback keeps routing graph-neutral
+    // by construction; clean files — 99.6%+ — stay on the fast path.
+    if tree.root_node().has_error() {
+        return Err("defer: parse tree contains errors — wasm recovery is canonical".to_string());
+    }
+
     let mut w = Walker {
         src: source,
         file_path,