feat(kernel): R7b Lua+Luau walker — one lua module, vendored-grammar-C lua v0.4.1, tree-sitter-luau 1.2.0 pin, both default-routed (#1384)

R7b batch 4 #2 (docs/design/lua-luau-kernel-port-checklist.md is the
authoritative quirk list). ONE walker for both dialects (ccpp precedent) —
the differences are exactly four: luau's type_definition aliases, the
`export `-slice isExported hook, the return-type signature suffix, and the
grammar handle.

Grammar prep is kernel-side only, no wasm change: lua is the SECOND
vendored-grammar-C language (the vendored wasm is the v0.4.1 tag, a revision
not on crates.io — tag artifacts compiled via build.rs, shas pinned); luau
is a plain crate pin =1.2.0 whose tarball is sha-identical to the tag (the
swift tag≠crate divergence does not recur). Grammar-parity rows replace the
bump gate entirely.

Preserved bug-for-bug (all probe-pinned): the require/visitNode-hook
ASYMMETRIES (top-level requires — including inside top-level if/for/while —
mint import nodes while the identical body-level statement emits
`calls "require"`; top-level `local x = foo()` initializers are invisible
while global `x = foo()` calls emit), the BFS string-win inside require args
(`require(script:WaitForChild("Kid"))` → import Kid) and Roblox instance
paths, receiver-QN methods (`M.sub.deep::chained`, `_G::installed`,
stack-QN nested globals like `render::leakedGlobal`), the raw-text callee
world (colon forms with `self` never stripped, bracket callees,
newline-glued chains byte-verbatim, the `(handler)` paren-conversion),
LUA_SPEC function-as-value capture with the `M.cb = cb` param-storage skip
and first-occurrence dedupe, LuaDoc `---` keeping a leading `- ` plus
`--!strict` joining docstring chains (block-comment docstrings keep interior
CRLF bytes), variable nodes at the IDENTIFIER with positional value pairing,
duplicate same-(kind,name,line) ids, and the lua↔luau isExported wire
divergence (lua functions: flag absent; luau functions: present-false;
methods: absent in both; variables: present-false in both; `export type`:
true).

Gates: parity sweeps first-run 0-diff on kong/lazy.nvim/lua-resty-core
(lua) + lune/Fusion (luau) — 1,734 clean files byte-parity, deferrals
1/0/0/3/8 matching the survey's both-arm predictions exactly (kong's 1 = a
deliberately invalid fixture; luau's = grammar-inherent generic type packs
and default type params); full-init dumps byte-identical kernel-vs-wasm ×4
(kong 157,650 dump lines); kernel-lua-parity suite (both torture fixtures +
in-memory CRLF variants + glue-chain, duplicate-id, and cross-dialect defer
pins + kernel-arm wire-flag pins); full suite 2,647 green ×2 with
CODEGRAPH_KERNEL_EXPECT=1. DEFAULT_ROUTED += lua, luau (18 langs).

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

codegraph-kernel/src/langs.rs

@@ -18,12 +18,17 @@ use tree_sitter::Language;
 extern "C" {
     fn tree_sitter_kotlin() -> *const ();
 }
+// Vendored lua grammar (build.rs-compiled C — the wasm's v0.4.1 revision is
+// not on crates.io; see grammars/lua and the lua-luau checklist).
+extern "C" {
+    fn tree_sitter_lua() -> *const ();
+}
 
 /// Languages this kernel binary can extract (reported by contractInfo;
 /// TS-side routing policy decides what actually routes).
-pub const LANGUAGES: [&str; 16] = [
+pub const LANGUAGES: [&str; 18] = [
     "typescript", "tsx", "javascript", "jsx", "java", "python", "go", "c", "cpp", "rust",
-    "csharp", "ruby", "php", "swift", "kotlin", "r",
+    "csharp", "ruby", "php", "swift", "kotlin", "r", "lua", "luau",
 ];
 
 pub fn grammar_for(language: &str) -> Option<Language> {
@@ -60,6 +65,14 @@ pub fn grammar_for(language: &str) -> Option<Language> {
         // R7b batch 4: crate =1.2.0, sha-identical to the r-lib v1.2.0 tag
         // the vendored wasm was built from (r checklist §Grammar prep).
         "r" => Some(tree_sitter_r::LANGUAGE.into()),
+        // R7b batch 4: v0.4.1 vendored C compiled in build.rs (revision not
+        // on crates.io — the wasm is the v0.4.1 tag, table-identical).
+        "lua" => {
+            Some(unsafe { tree_sitter_language::LanguageFn::from_raw(tree_sitter_lua) }.into())
+        }
+        // R7b batch 4: crate =1.2.0, sha-identical to the v1.2.0 tag the
+        // vendored wasm was built from (lua-luau checklist §Grammar prep).
+        "luau" => Some(tree_sitter_luau::LANGUAGE.into()),
         _ => None,
     }
 }