feat(kernel): R7b Kotlin walker — kotlin module, vendored-grammar-C build, kotlin default-routed (#1382)

Sixth R7b port — the T1½ batch finale. Checklist-first recipe
(docs/design/kotlin-kernel-port-checklist.md, 1,121 lines, dist-extractor
ground truth); parity passed FIRST RUN on all three repos.

THE NOVEL MECHANISM — vendored-grammar-C (the §4 tracker's prescription,
first use): the crates.io tree-sitter-kotlin 0.3.8 pins `tree-sitter >= 0.21,
< 0.23` (the kernel links 0.25) and tree-sitter-kotlin-ng is a DIFFERENT
grammar (8 fields vs 0, renamed kinds — extractor-breaking), so no crate dep
is possible. The fwcd 0.3.8 tag's sha-matched parser.c + scanner.c are
vendored into codegraph-kernel/grammars/kotlin and compiled by build.rs (cc),
exposed via tree-sitter-language::LanguageFn. The wasm re-vendor is
behavior-NEUTRAL (0 CST/error disagreements across 1,984 gate-repo files;
old-vs-new full-init dumps byte-identical ×3) — a reproducibility re-vendor,
ABI stays 14.

Walker firsts: extension-function receivers (getReceiverType →
`WidgetK::extend` QN OVERRIDE with no package prefix, the qualified-receiver
`com::qext` first-segment bug, and the owner-contains fallback that excludes
`interface` kinds and is source-order dependent) and extractModifiers
(expect/actual platform modifiers → the node DECORATORS wire field on every
created node — the KMP synthesizer's feed, incl. `actual typealias`).
Preserved bug-for-bug: the FIELD_COUNT-0 dead cluster (no signatures, ZERO
type-annotation refs), hook-consumed property initializers emitting nothing
(incl. `by lazy {}`), the bodiless-vs-bodied class header asymmetry, enum-
entry bodies being invisible, KDoc never a docstring AND chain-breaking,
comment-gluing into import/package extents, `@Anno(args)` emitting nothing
while `@Marker` decorates, zero instantiates refs, the paren-then-lambda
`trailing()` garbage callee, text-includes visibility/suspend false
positives, and the packaged-file value-ref target drop. The fun-interface
misparse-recovery hook is DEFER-SHIELDED (every such file has_error) and
deliberately not ported. The swift-sweep lesson pre-applied: the shared
`assignment` shadow-prune case is implemented alongside the
property_declaration case.

Gates: sweeps 0-diff okio 299/322, okhttp 531/580, kotlinx.coroutines
1031/1082 (deferrals exactly the predicted 23/49/51 — both-arm grammar
reality incl. PHANTOM hasError files with complete CSTs; the kernel trusts
the flag); full-init dumps byte-identical ×3 (46.5k/108.9k/92.3k lines); KMP
expect/actual synthesis IDENTICAL across arms (412 edges on
kotlinx.coroutines — the tracker's KMP validation); kernel-kotlin-parity
suite (torture reflowed off the phantom shapes + .kts script + CRLF variants
+ fun-interface and phantom defer pins) + kotlin grammar-parity row (the
C-build ↔ wasm table identity proof); full suite 2,633 green ×2 under
CODEGRAPH_KERNEL_EXPECT=1. DEFAULT_ROUTED += kotlin (15 langs).

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

docs/design/kotlin-kernel-port-checklist.md

@@ -1,6 +1,16 @@
 # Kotlin kernel port (R7b) — the bug-for-bug checklist
 
-**Status: SURVEY COMPLETE (2026-07-20) — PORT NOT STARTED.** Survey basis: every
+**Status: PORT COMPLETE (2026-07-20)** — walker `codegraph-kernel/src/kotlin.rs`
++ the vendored-grammar-C build (codegraph-kernel/grammars/kotlin via build.rs
+cc — the mechanism's first use), all gates passed (bump dumps byte-identical
+old-vs-new ×3 as predicted; parity sweeps 0-diff okio 299/322 / okhttp
+531/580 / kotlinx.coroutines 1031/1082 with exactly the predicted 23/49/51
+deferrals; kernel-arm dumps byte-identical ×3; KMP expect/actual synthesis
+IDENTICAL — 412 edges both arms; kernel-kotlin-parity suite; DEFAULT_ROUTED
++= kotlin — 15 languages). One fixture note: the survey's torture.kt itself
+tripped the PHANTOM-error class (one-line class/object bodies) and deferred —
+the checked-in parity fixture reflows those to multi-line, and the phantom
+shape is pinned in the defer test instead. Survey basis: every
 TS-side branch a `.kt`/`.kts` file exercises, with file:line anchors as of
 **`a6c62d7`** (HEAD at survey time, clean main). Every grammar-shape claim below
 was **probed against both the production tree-sitter-wasms build and a fresh

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

@@ -609,7 +609,7 @@ 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. | ☑ |
 | 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. | ☐ |
-| kotlin | `languages/kotlin.ts` | T1½ | crates.io | Expect/actual pairing is synthesis-side (fine); extraction is clean but validate against a KMP repo. | ☐ |
+| 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. | ☑ |
 | metal, cuda | dialects over the cpp grammar | **T2** (rides c/cpp) | crates.io (cpp) | **DONE (rides R7a)** — `.metal`/`.cu`/`.cuh` map to 'cpp' and their blanks run in the hoisted preParse (filePath rides along for the extension gates); hoist-parity pinned in kernel-ccpp-parity.test.ts + the metal/cuda suites. | ☑ |