feat(kernel): R1 scaffold — napi-rs extraction kernel, buffer contract, routing + fallback, grammar-parity CI

Phase 0 of the Rust extraction-kernel migration (docs/design/
rust-kernel-migration-plan.md, now checked in with §3a recording the
shipped state):

- codegraph-kernel/ napi-rs crate: extractFile(path, content, language)
  → five flat buffers (meta/nodes/edges/refs/arena), one JS boundary
  crossing per file. Node ids computed Rust-side, byte-identical to
  generateNodeId (pinned by test vector). Reserved per-node metrics slot
  for the Arc 3.2 code-metrics work.
- Generic .scm-driven emitter (@def.<kind>/@name/@ref.<kind> captures,
  byte-range scope stack → ::-joined qualified names, contains edges,
  refs attributed to the innermost enclosing symbol). Seed TS/JS queries
  are smoke-level; R2 replaces them with the full port.
- Routing seam in extractFromSource with per-file wasm fallback.
  DEFAULT_ROUTED is empty — no behavior change until a language passes
  its equivalence gate (R3). Dev opt-in: CODEGRAPH_KERNEL_LANGS. Kill
  switch: CODEGRAPH_KERNEL=0. Loader verifies ABI + kind tables before
  routing; EDGE_KINDS became a runtime array because kind order is now
  wire contract.
- Grammar-source parity: vendored TS/TSX/JS wasm grammars built from the
  exact crate revisions (tree-sitter-typescript v0.23.2,
  tree-sitter-javascript v0.25.0, checked-in parser.c, ts-cli 0.25.10) —
  the tree-sitter-wasms builds were 2023-era, which the new
  kernel-grammar-parity test caught on day one. Production TS/JS parsing
  gets 2.5 years of grammar fixes; full suite green (2456 tests).
- Build/release wiring: scripts/build-kernel.sh + npm run build:kernel;
  release.yml kernel prebuild matrix (continue-on-error — the kernel is
  optional everywhere, bundles fall back to the wasm path); bundles stage
  lib/kernel/codegraph-kernel.node; release job runs the kernel suites
  with CODEGRAPH_KERNEL_EXPECT=1.

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

src/types.ts

@@ -14,6 +14,10 @@
  * Defined as a runtime-iterable `as const` array so the same source
  * of truth backs both the TS type and any runtime validation
  * (e.g. the search query parser).
+ *
+ * The ARRAY ORDER is part of the native kernel's wire contract (kinds cross
+ * the boundary as indexes — see src/extraction/kernel/layout.ts); append new
+ * kinds, never reorder.
  */
 export const NODE_KINDS = [
   'file',
@@ -43,21 +47,28 @@ export const NODE_KINDS = [
 export type NodeKind = (typeof NODE_KINDS)[number];
 
 /**
- * Types of edges (relationships) between nodes
+ * Types of edges (relationships) between nodes.
+ *
+ * Runtime-iterable like NODE_KINDS. The ARRAY ORDER is part of the native
+ * kernel's wire contract (kinds cross the boundary as indexes — see
+ * src/extraction/kernel/layout.ts); append new kinds, never reorder.
  */
-export type EdgeKind =
-  | 'contains'        // Parent contains child (file→class, class→method)
-  | 'calls'           // Function/method calls another
-  | 'imports'         // File imports from another
-  | 'exports'         // File exports a symbol
-  | 'extends'         // Class/interface extends another
-  | 'implements'      // Class implements interface
-  | 'references'      // Generic reference to another symbol
-  | 'type_of'         // Variable/parameter has type
-  | 'returns'         // Function returns type
-  | 'instantiates'    // Creates instance of class
-  | 'overrides'       // Method overrides parent method
-  | 'decorates';      // Decorator applied to symbol
+export const EDGE_KINDS = [
+  'contains',        // Parent contains child (file→class, class→method)
+  'calls',           // Function/method calls another
+  'imports',         // File imports from another
+  'exports',         // File exports a symbol
+  'extends',         // Class/interface extends another
+  'implements',      // Class implements interface
+  'references',      // Generic reference to another symbol
+  'type_of',         // Variable/parameter has type
+  'returns',         // Function returns type
+  'instantiates',    // Creates instance of class
+  'overrides',       // Method overrides parent method
+  'decorates',       // Decorator applied to symbol
+] as const;
+
+export type EdgeKind = (typeof EDGE_KINDS)[number];
 
 /**
  * Supported programming languages. See NODE_KINDS for why this is a