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/Cargo.lock

@@ -60,6 +60,7 @@ dependencies = [
  "tree-sitter-java",
  "tree-sitter-javascript",
  "tree-sitter-language",
+ "tree-sitter-luau",
  "tree-sitter-php",
  "tree-sitter-python",
  "tree-sitter-r",
@@ -558,6 +559,16 @@ version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "009994f150cc0cd50ff54917d5bc8bffe8cad10ca10d81c34da2ec421ae61782"
 
+[[package]]
+name = "tree-sitter-luau"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "871abeb427d719788bb38094facd7ff082908ef2b93c1d3d6a5f6025330120f4"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
 [[package]]
 name = "tree-sitter-php"
 version = "0.24.2"