feat(kernel): R7b R walker — rlang module, tree-sitter-r 1.2.0 crate pin, r default-routed (#1383)

R7b batch 4 #1 (docs/design/r-kernel-port-checklist.md is the authoritative
quirk list; survey + probe record therein). The lightest-shared-surface,
heaviest-hook port: languages/r.ts works entirely through the visitNode hook
(every type list empty except callTypes:['call']), so the walker is a file
node + a faithful hook transcription + the generic extractCall + pre-order
recursion — four shared machineries (value-refs, static-member reads, type
annotations, fn-ref capture) are dead by language gates and stay dead.

Grammar prep is the first true no-op of the arc: the crates.io tree-sitter-r
1.2.0 tarball ships parser.c AND scanner.c sha-identical to the r-lib v1.2.0
tag the vendored wasm was built from — crate pin only, no wasm change, no
bump gate; kernel-grammar-parity gains the r row (ABI 14, same-revision).

Preserved bug-for-bug (all probe-pinned): calls "return" on every return(x)
(named node in v1.2.0), the import quintet's silent dynamic-arg consumption
vs class/generic fall-through asymmetry, library(help = pkg) importing the
named arg, class-idiom variable suppression by callee name, chained/right-
assign/precedence-ghost gaps, env$fn body-leak-to-file, raw-text callees
verbatim (pkg::fn, obj$meth, "strfn" quotes kept, (handler) conversion),
duplicate same-(kind,name,line) ids, roxygen dropped entirely, UTF-16
columns/slices.

Gates: parity sweeps first-run 0-diff on AnomalyDetection/dplyr/ggplot2/
shiny (838 files; deferrals exactly 0/0/0/1 — the 1 is the moustache-
template pseudo-R file, both-arm) — kernel-parity.mjs gained lowercased-
extension matching so .R files sweep (matches detectLanguage routing);
full-init dumps byte-identical kernel-vs-wasm on dplyr/ggplot2/shiny;
kernel-r-parity suite (torture fixture + in-memory CRLF + BOM variants +
defer pin + kernel-arm quirk pins); full suite 2,638 green ×2 with
CODEGRAPH_KERNEL_EXPECT=1. DEFAULT_ROUTED += r (16 langs).

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

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

@@ -608,7 +608,8 @@ parity before porting the language.
 | php | `languages/php.ts` | T1 | crates.io | **DONE (R7b #4, 2026-07-20)** — `php.rs` walker (LANGUAGE_PHP, never PHP_ONLY); grammar bumped to v0.24.2 (crate + vendored wasm together; NOT graph-neutral — bump gate = enumerate+classify: anon-class wrapper, grouped nested-clause skip, old-error files, the survey-missed 8.4 `new X()->m()` misparse fix, everything else proven resolution ripple via ref↔edge pairing). Parity 0-diff monolog/laravel-framework/symfony (13,950 files) + dump byte-identical ×3. Trait-use implements refs ride REF_FLAG_FILE_PATH. Quirk list: docs/design/php-kernel-port-checklist.md. | ☑ |
 | 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. | ☑ |
-| dart, scala, lua, luau, r | dedicated files | T1 | crates.io (luau/r/scala: verify crate freshness vs our wasm) | Long-tail T1; port opportunistically after the big five. | ☐ |
+| 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. | ☐ |
 | 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. | ☑ |