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>

docs/design/rust-kernel-migration-plan.md

@@ -609,7 +609,8 @@ parity before porting the language.
 | csharp | `languages/csharp.ts` | T1 | crates.io | **DONE (R7b #2, 2026-07-20)** — `csharp.rs` walker; NO grammar bump (the #717 vendored wasm verified table-identical to crate 0.23.5 — first port with no grammar-prep step); the #237 `#if` preParse stays TS-side via the route-point hoist. Parity 0-diff on serilog/Newtonsoft.Json/jellyfin (3,229 files) + dump byte-identical ×3; deferral 0.05–3.3% = both-arm `#if` damage. Quirk list: docs/design/csharp-kernel-port-checklist.md. | ☑ |
 | rust | `languages/rust.ts` | T1 | crates.io | **DONE (R7b #1, 2026-07-20)** — `rustlang.rs` walker; grammar bumped to v0.24.2 (crate + vendored wasm together). Parity 0-diff on ripgrep/tokio/rust-analyzer + dump byte-identical ×3; rust-analyzer's parser crates defer 18% (token-macro tables, both-arm parse errors — grammar-inherent). Quirk list: docs/design/rust-lang-kernel-port-checklist.md. | ☑ |
 | r | `languages/r.ts` | T1 | crates.io | **DONE (R7b batch 4 #1, 2026-07-20)** — `rlang.rs` walker; NO grammar change (crate pin `=1.2.0`: the crates.io tarball ships parser.c AND scanner.c sha-identical to the r-lib v1.2.0 tag the vendored wasm was built from — first true no-op grammar prep). The lightest-shared-surface, heaviest-hook port: r.ts works entirely through visitNode (every type list empty but `callTypes`), four shared machineries dead by language gates, walker = file node + hook transcription + generic extractCall. Parity 0-diff on AnomalyDetection/dplyr/ggplot2/shiny (838 files, deferrals 0/0/0/1 — the 1 = a moustache-template pseudo-R file, both-arm) + dump byte-identical ×3 (dplyr/ggplot2/shiny). kernel-parity.mjs gained lowercased-extension matching (`.R` is the dominant casing). Quirk list: docs/design/r-kernel-port-checklist.md. | ☑ |
-| dart, scala, lua, luau | dedicated files | T1 | dart/scala/lua: **vendored C** (revs not on crates.io — batch-4 probe); luau: crates.io `=1.2.0` | Long-tail T1, surveys COMPLETE 2026-07-20 (checklists in docs/design/). dart = tree-sitter-wasms artifact byte-copy re-vendor + UserNobody14 d4d8f3e vendored-C; scala = master 0aca5d0a6f vendored-C (35MB parser.c); lua+luau share one walker module. | ☐ |
+| lua, luau | `languages/lua.ts` + `luau.ts` (36-line extension) | T1 | lua: **vendored C** (v0.4.1 not on crates.io); luau: crates.io `=1.2.0` (tag≡crate sha-verified) | **DONE (R7b batch 4 #2, 2026-07-20)** — ONE walker (`lua.rs`, ccpp-style dialect flag); lua = the second vendored-grammar-C language (v0.4.1 tag artifacts, shas in the checklist); luau = plain crate pin. NO wasm change for either — grammar-parity rows replace the bump gate. Ports the require/visitNode-hook asymmetries (top-level imports vs body `calls "require"`), receiver-QN methods, the top-level initializer-visibility inversion, raw-text callee world (colon/bracket/glue chains, paren-conversion), LUA_SPEC fn-ref capture, LuaDoc `- `-keeping docstrings, and the lua↔luau isExported wire divergence. Parity 0-diff kong/lazy.nvim/lua-resty-core/lune/Fusion (1,734 clean files; deferrals 1/0/0/3/8 — every one matching the survey's both-arm predictions) + dump byte-identical ×4 (kong 157,650 dump lines). Quirk list: docs/design/lua-luau-kernel-port-checklist.md. | ☑ |
+| dart, scala | dedicated files | T1 | **vendored C** (revs not on crates.io — batch-4 probe) | Long-tail T1, surveys COMPLETE 2026-07-20 (checklists in docs/design/). dart = tree-sitter-wasms artifact byte-copy re-vendor + UserNobody14 d4d8f3e vendored-C (sibling-body double-walk is the port hazard); scala = master 0aca5d0a6f vendored-C (35MB parser.c; phantom-hasError dominant on scala-3). | ☐ |
 | kotlin | `languages/kotlin.ts` | T1½ | **vendored C** (crate unusable) | **DONE (R7b #6, 2026-07-20)** — `kotlin.rs` walker; the arc's FIRST vendored-grammar-C language: fwcd 0.3.8's sha-matched parser.c/scanner.c compile inside codegraph-kernel via build.rs + cc (the crates.io crate pins tree-sitter <0.23; tree-sitter-kotlin-ng is a different grammar). Behavior-neutral wasm re-vendor (dumps byte-identical old-vs-new ×3). Two walker firsts: extension-fn receiver QNs + owner-contains, and extractModifiers→decorators (KMP expect/actual — 412 synthesized edges identical both arms on kotlinx.coroutines). Parity 0-diff okio/okhttp/kotlinx.coroutines (1,861 clean files; deferral 4.7–8.5% both-arm incl. PHANTOM hasError files). Quirk list: docs/design/kotlin-kernel-port-checklist.md. | ☑ |
 | swift | shared + dedicated branch | T1½ | crates.io | **DONE (R7b #5, 2026-07-20)** — `swift.rs` walker incl. the #1020 dedicated property branch (Alamofire's 348 property nodes reproduced exactly on the kernel arm); grammar bumped to crate 0.7.3 (wasm built from the CRATE TARBALL's src — the tag ships an older ABI-14 generation; delta = error-set membership + 2 gate-found categories, all classified). Parity 0-diff Alamofire/vapor/swift-nio (720 clean files; deferral 9–27% both-arm structural — sweeps use --max-deferral 0.3). One walker fix found by the sweep: the shared `assignment` shadow-prune case is swift-live (declared-then-assigned `let X: T`). Quirk list: docs/design/swift-kernel-port-checklist.md. | ☑ |
 | c, cpp | `languages/c-cpp.ts` | **T2** | crates.io | **DONE (R7a, 2026-07-17)** — `ccpp/` walker; ALL pre-passes stayed TS-side via the route-point preParse hoist (+6 new blanks added during gating — see the checklist doc); content-based `.h` C-vs-C++ detection stays upstream at detectLanguage. Parity 0-diff + dump byte-identical on redis/git/fmt/protobuf/ALS. | ☑ |