[takeokunn]

Summary

Split the JavaScript implementation and tests into feature packages. Each feature package owns its grammar registrations; the shared syntax package remains independent of language feature packages.

Feature	Scope
syntax	Lexer, shared parser core, automatic semicolon insertion, and grammar registry
expressions	Expression grammar and runtime operators
statements	Statement grammar and control flow
functions	Function grammar, calls, and function runtime hooks
classes	Class grammar, lowering, and runtime
objects	Ordinary object and prototype behavior
proxies	Proxy behavior
iterators	Iterators and generators
async	Promises and async built-ins
modules	Module grammar and runtime
regex	Regular expressions
strings	Strings, templates, encoding, and URL built-ins
numbers	Number lexing, math, and BigInt
arrays	Arrays and typed arrays
json	JSON
dates	Date and Temporal
intl	Internationalization built-ins
errors	Error built-ins and exceptions
disposables	Explicit resource management and using
backend	Host built-ins, runtime dispatch, and VM integration
v8-objects	V8-specific object representations introduced by PR #9

The ASDF load order, feature dependency metadata, test packages, and feature glossary now follow this split. Test files now live in their feature packages.

Verification

Check	Before	After
JavaScript test inventory	1,109 tests loaded from the baseline system	1,109 tests; 1,109 passed, 0 skipped, 0 todo, 0 failed, 0 errored
Umbrella JavaScript integration suite	955 passed, 26 expected-failed, 981 total	955 passed, 26 expected-failed, 981 total; expected-failure IDs and order match

• scripts/with-timeout.pl 900 sbcl --script run-tests.lisp: 1,109 passed.
• feature-lint: 21 features, checks 1–7 passed.
• orphan-tests: 79 found, 75 registered, 4 allowlisted, 0 orphan.
• treefmt and maxFileLength: passed.
• The local docs derivation is available only for x86_64-linux, while this workstation is aarch64-darwin; branch CI will verify the docs gate.