feat(kernel): R7b Scala walker — scala module, vendored-grammar-C master@0aca5d0a6f, scala default-routed (#1385)

R7b batch 4 #3 (docs/design/scala-kernel-port-checklist.md is the
authoritative quirk list). The third vendored-grammar-C language and the
biggest grammar in the tree (35MB parser.c): the vendored wasm is
tree-sitter/tree-sitter-scala master@0aca5d0a6f — a post-v0.26.0 generation
sync that is not a release (the 0.26.0 crate is 30 states BEHIND, so a
crate pin would be a silent downgrade). NO wasm change: production has
parsed with this exact revision since #91 — the kernel-grammar-parity row
(ABI 15, 26,650 states, 32 fields, id-by-id tables) is the whole alignment
proof.

Preserved bug-for-bug (all probe-pinned): the leak-through asymmetries —
extension methods mint NO nodes (first def's body calls leak to the
enclosing scope, later defs invisible, and the braced form resolves its
body field to the `{` TOKEN via first-match-wins field lookup → whole
extension invisible); anonymous `new T { … }` template_body members leak to
the enclosing scope (findAnonymousClassBody misses template_body); the
bodied-vs-bodiless class asymmetry (bodiless headers walk class_parameters
→ default-value calls emit FROM the class; bodied ones never see them) —
plus first-segment import names (`import com.example.C` → `com`), the
val/var hook keyed on the enclosing-definition NODE TYPE (object vals →
constants/value-ref targets, class/trait/enum/given vals → fields) with
consumed initializers, every def routed through extractMethod with the
top-level function fallback, nested defs in bodies minting NOTHING (the
inverse of kotlin) while body-local classes extract fully, curried
signatures keeping only the FIRST parameter list (type params win the
`parameters` field), enum cases positioned at the CASE node with invisible
params/extends tails, extends with-chains via scalaBaseTypeName,
`@deprecated(args)` decorates, the #750 capitalized-chain re-encode
(`WidgetS.create().render`), literal-receiver silence, static-member reads
AND writes, infix invisibility, `derives` silence, scaladoc retention with
the CRLF `\r` pin, full value-reference machinery (shadow prune, last-wins
same-name targets, `$X`/`${X}` interpolation reads), and SCALA_SPEC
fn-refs (bare ids + postfix eta unwrap + varinit, var-init non-capture).

Gates: parity sweeps first-run 0-diff on os-lib/cats/scala3-compiler-src/
scala3-library-src — 1,935 clean files byte-parity, deferrals 0/15/57/116
matching the survey's predictions exactly (scala-3's PHANTOM hasError
files — flag-true, zero ERROR nodes, capture-checking `^` — defer on the
FLAG); full-init dumps byte-identical ×3 (os-lib, cats, scala3 whole-repo
950,889 dump lines); kernel-scala-parity suite (9 fixtures + 9 in-memory
CRLF variants incl. Scala-3 indentation through the external scanner +
phantom/real-error defer pins + first-segment/namespace/value-ref pins);
full suite 2,669 green ×3 with CODEGRAPH_KERNEL_EXPECT=1
(kernel-scaffold's stays-wasm example moved scala → pascal).
DEFAULT_ROUTED += scala (19 langs).

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

CHANGELOG.md

@@ -11,7 +11,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### New Features
 
-- Indexing TypeScript, TSX, JavaScript, JSX, Java, Python, Go, C, C++, Rust, C#, Ruby, PHP, Swift, Kotlin, R, Lua, and Luau projects is faster: parsing and symbol extraction now run in a native engine when a prebuilt binary is available for your platform (release bundles include one), producing exactly the same graph — verified byte-for-byte against the previous engine on real repositories, from small libraries up to vscode-, dubbo-, django-, git-, protobuf-, tokio-, rust-analyzer-, jellyfin-, rails-, symfony-, swift-nio-, kotlinx.coroutines-, ggplot2-, and Kong-scale codebases (Lombok-generated members, C function-pointer tables, and Unreal-Engine-style macro-heavy headers included; CUDA and Metal sources ride the C++ path). The speedup is largest on resource-constrained machines like CI runners. No setup needed: platforms without the native binary, and individual files with syntax errors, automatically use the previous engine, and `CODEGRAPH_KERNEL=0` turns the native path off entirely.
+- Indexing TypeScript, TSX, JavaScript, JSX, Java, Python, Go, C, C++, Rust, C#, Ruby, PHP, Swift, Kotlin, Scala, R, Lua, and Luau projects is faster: parsing and symbol extraction now run in a native engine when a prebuilt binary is available for your platform (release bundles include one), producing exactly the same graph — verified byte-for-byte against the previous engine on real repositories, from small libraries up to vscode-, dubbo-, django-, git-, protobuf-, tokio-, rust-analyzer-, jellyfin-, rails-, symfony-, swift-nio-, kotlinx.coroutines-, ggplot2-, Kong-, and Scala-3-compiler-scale codebases (Lombok-generated members, C function-pointer tables, and Unreal-Engine-style macro-heavy headers included; CUDA and Metal sources ride the C++ path). The speedup is largest on resource-constrained machines like CI runners. No setup needed: platforms without the native binary, and individual files with syntax errors, automatically use the previous engine, and `CODEGRAPH_KERNEL=0` turns the native path off entirely.
 - Reference resolution now runs in parallel on large projects. When a project has enough pending references to make it worthwhile (roughly 150k+, typical for big Java/Kotlin/Spring codebases), resolution fans out across worker threads while results are applied in the exact order the single-threaded path would have used — the graph comes out byte-for-byte identical, about twice as fast end-to-end on a 4,000-file Java project in our testing. Small projects keep the single-threaded path automatically (the fan-out costs more than it saves there). Set `CODEGRAPH_NO_PARALLEL_RESOLVE=1` to disable, or `CODEGRAPH_PARALLEL_RESOLVE_MIN=<count>` to tune when it engages.
 - Indexing large projects got another sizeable speedup — about a quarter less wall-clock on the same 4,000-file Java project, with the graph still byte-for-byte identical. Two changes: the database no longer interleaves expensive checkpoint housekeeping into the middle of resolution on a fresh index (it's folded once at the end instead), and while one batch's results are being written out, the worker threads are already resolving the next batch instead of sitting idle.
 - The dynamic-dispatch analysis that runs at the end of indexing (callback, event, and framework wiring) now runs its passes in parallel on large projects, cutting that stage roughly in half there — and a pass that crashes now retries safely instead of failing the whole index, which also makes very large codebases that previously died in this stage more likely to index to completion. Graphs remain byte-for-byte identical.