feat(kernel): R7b Dart walker — dart module, vendored-grammar-C d4d8f3e + wasm byte-copy vendor, dart default-routed (#1386)

R7b batch 4 #4 — the FINAL R7b language (docs/design/dart-kernel-port-checklist.md
is the authoritative quirk list). The fourth vendored-grammar-C language,
with a twist: production dart resolved its wasm from tree-sitter-wasms,
whose dart dependency is an UNPINNED github:UserNobody14/tree-sitter-dart —
a routine dependency update would have silently changed dart's grammar.
This PR byte-copies the shipping 0.1.13 artifact into src/extraction/wasm/
(VENDORED_WASM_LANGS += dart) and compiles the same-commit (d4d8f3e337d8)
parser.c/scanner.c in the kernel — table identity proven by the
kernel-grammar-parity row. crates.io tree-sitter-dart is the nielsenko
fork (different lineage) — rejected.

The center of gravity is THE SIBLING-BODY DOUBLE-WALK, reproduced
bug-for-bug: dart attaches every function/method body as a NEXT SIBLING of
its signature, and the TS walkers consume each body TWICE — once via
resolveBody (attributed to the function/method) and once via the enclosing
generic walk (attributed to the file/class). Duplicate local-function
nodes with the SAME id under different parents, duplicated
calls/instantiates refs, and file/class-attributed fn-ref twins all emit
in the exact observed interleave (a dedicated fixture pins the
duplicate-id rows; the bloc kind-census spot-check pins the counts).

Also preserved (probe-pinned): the extractBareCall selector matrix (the
first callTypes=[] language — cascades completely invisible, `?.` encodes
like `.`, the `ConfigT.load()` calls+references double emission with no
callee-of-call skip, capitalized-chain `Foo.create().run` re-encode,
const-object callee names); the constructor hooks (unnamed ctor skipped,
named ctors/factories renamed to the CTOR name with the class as
returnType, `@override (T) m()` record-misparse rescued by class-name
validation); operator methods minting `method "<anonymous>"`;
static_final_declaration constants via the visitNode hook while instance
fields mint NOTHING; the prefixed-return-type prefix bug (`other.OtherClass
f()` → returnType `other`); enum `with` mixins silent vs `implements`
working; anonymous extensions named after the ON type; deferred imports
invisible; named-argument callbacks NOT fn-ref-captured (the Flutter
`onPressed:` idiom — future accuracy PR, TS-side first); `async*`/`sync*`
NOT async; value-refs with the LIVE dart sibling-body pull and the
`$X`-vs-`${X}` interpolation asymmetry; dartdoc kept in all three comment
forms with the annotation-broken chain.

Gates: parity sweeps first-run 0-diff on shelf/bloc/flutter — 5,815 clean
files byte-parity, deferrals 10/21/1341 ≈ the survey's 10/21/~1340
(both-arm grammar reality: empty object patterns — the sealed-class
idiom — and unnamed `library;` dominate; --max-deferral 0.3); full-init
dumps byte-identical ×3 (shelf 7,959 / bloc 40,026 / flutter 1,855,319
dump lines); bloc per-kind node census identical across arms (the
double-walk duplicate rows survive the store identically);
kernel-dart-parity suite (7 fixtures + in-memory CRLF variants +
double-walk duplicate-id pin + generated-file skip pin + two defer pins);
full suite 2,688 green ×2 with CODEGRAPH_KERNEL_EXPECT=1.
DEFAULT_ROUTED += dart (20 langs — R7b COMPLETE).

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

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

@@ -611,7 +611,7 @@ parity before porting the language.
 | 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. | ☑ |
 | 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. | ☑ |
 | scala | `languages/scala.ts` | T1 | **vendored C** (master@0aca5d0a6f — not a release; crate 0.26.0 is 30 states behind) | **DONE (R7b batch 4 #3, 2026-07-20)** — `scala.rs` walker; the third vendored-grammar-C language (35MB parser.c — the biggest grammar in the tree). NO wasm change (production has parsed with this exact revision since #91) — the grammar-parity row is the whole alignment proof. Ports the leak-through asymmetries (extension first-def call leak + braced-form invisibility via the `{`-token body field, anon `new T {…}` template_body member leaks, bodied-vs-bodiless class_parameters), first-segment import names, the val/var hook's enclosing-NODE-TYPE kinds, defs-as-methods with top-level function fallback, nested-def invisibility, curried/type-params-first signatures, the #750 capitalized re-encode, static-member WRITES, scaladoc retention, full value-refs (last-wins targets) + SCALA_SPEC fn-refs (varinit + postfix eta). Parity 0-diff os-lib/cats/scala3-compiler-src/scala3-library-src (1,935 clean files; deferrals 0/15/57/116 — every count matching the survey exactly; scala-3 PHANTOM hasError deferred on the flag) + dump byte-identical ×3 (scala3 whole-repo 950,889 dump lines). Quirk list: docs/design/scala-kernel-port-checklist.md. | ☑ |
-| dart | `languages/dart.ts` | T1 | **vendored C** (UserNobody14 d4d8f3e — reached via tree-sitter-wasms' unpinned github dep) | Long-tail T1, survey COMPLETE 2026-07-20 (docs/design/dart-kernel-port-checklist.md). Port = vendored-C + byte-copy the tree-sitter-wasms wasm artifact into src/extraction/wasm/ (kills the unpinned-dep hazard). The sibling-body DOUBLE-WALK (duplicate ids, ×3 refs) is the port hazard; sweeps --max-deferral 0.3. | ☐ |
+| dart | `languages/dart.ts` | T1 | **vendored C** (UserNobody14 d4d8f3e; wasm = the byte-copied tree-sitter-wasms 0.1.13 artifact, same commit) | **DONE (R7b batch 4 #4, 2026-07-20 — the FINAL R7b language)** — `dart.rs` walker; the fourth vendored-grammar-C language. The wasm byte-copy into src/extraction/wasm/ + VENDORED_WASM_LANGS kills tree-sitter-wasms' UNPINNED github-dep hazard (crates.io dart is a different-lineage fork — rejected). Ports THE SIBLING-BODY DOUBLE-WALK bug-for-bug (duplicate local-fn nodes sharing an id under different parents, duplicated calls/instantiates, file/class fn-ref twins — pinned by a dedicated fixture + the bloc kind-census spot-check), the extractBareCall selector matrix (first callTypes=[] language; cascades invisible, `?.`≡`.`, the `ConfigT.load()` calls+references double emission, capitalized-chain re-encode), the constructor naming/skip hooks (unnamed ctor skipped; named ctors renamed with class-as-returnType), operator methods as `<anonymous>`, static_final_declaration constants via the hook (instance fields mint nothing), prefixed-return-type prefix bug, enum-with silence, anonymous extensions named after the ON type, deferred-import invisibility, named-arg fn-ref non-capture, async*/sync*≠async, value-refs with the LIVE sibling-body pull. Parity 0-diff shelf/bloc/flutter (5,815 clean files; deferrals 10/21/1341 ≈ the survey's 10/21/~1340 — both-arm empty-object-pattern + `library;` reality, --max-deferral 0.3) + dump byte-identical ×3 (flutter 6,472 dart files) + bloc census identical per kind. Quirk list: docs/design/dart-kernel-port-checklist.md. | ☑ |
 | 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. | ☑ |