BEAM-native JS engine and compiler

[dannote]

Adds a second QuickJS execution backend that runs decoded QuickJS bytecode on the BEAM, plus an experimental compiler path that lowers QuickJS bytecode to BEAM modules.

Public API and runtime modes

• mode: :beam support for running JavaScript through the BEAM VM backend
• mode: :auto compiler-backed execution with fallback
• strict compiler audit mode via mode: :beam_compiler
• QUICKBEAM_MODE=beam_compiler support for audit runs
• raw BEAM disassembly for the :beam backend via QuickBEAM.disasm/2
• runtime/context integration, handler dispatch, module loading, dynamic import, globals, and interop for the VM path
• stack traces, source positions, and Error.captureStackTrace

Bytecode VM

• QuickJS bytecode decoder in Elixir
• BEAM interpreter for QuickJS bytecode
• control-flow, stack-depth, type, and diagnostics analysis passes
• local/argument/capture slot handling, including large-frame tuple mode
• generator and async-generator execution support
• promise scheduling and continuation state
• runtime invocation helpers for compiled and interpreted functions

Compiler backend

• hybrid compiler from QuickJS bytecode to BEAM modules
• block lowering, CFG analysis, stack-depth inference, type inference, and optimizer passes
• compiled runtime helpers for arithmetic, coercion, calls, construction, refs, globals, with-scope, iterators, objects, classes, promises, generators, and errors
• strict compiler-vs-interpreter audit harnesses and semantic corpus benches
• compiler opcode coverage reporting
• compiler perf/ROI benchmark

JavaScript semantics covered

• Object, Array, Function, String, Number, Boolean
• Math, JSON, Date, RegExp
• Map, Set, WeakMap, WeakSet, collection iterators, and self-iterability
• Symbol, well-known symbols, property keys, and Symbol.toStringTag
• Promise, async / await, generators, delegated yield*, and async generators
• Proxy and Reflect, including descriptor/prototype/extensibility invariants
• TypedArray, ArrayBuffer, BigInt
• classes, inheritance, super, private fields, private methods, private accessors, static private members, brand checks, and constructor return semantics
• descriptors, Object.create, Object.assign, Object.fromEntries, freeze/seal/preventExtensions/isExtensible/isFrozen/isSealed
• array expando properties, sparse arrays, callbacks, iterators, destructuring, spread, rest/default parameters, and arguments basics
• eval, with, refs, globals, callback/global write freshness, delete semantics, in, instanceof, new, update operators, arithmetic/coercion edge cases, and BigInt operations
• try/catch/finally, QuickJS gosub/ret finally control flow, nested catches inside finally, break/continue through finally, and catch-region slot preservation
• for-in enumeration mutation and nullish object coercion for with/destructuring
• Web API and Node-compat runtime integration used by the VM path

Static analysis and cleanup

• updated ex_dna, ex_slop, and credo
• mix lint now runs ExDNA with a zero-clone budget
• clone debt removed across VM runtime helpers, parser helpers, Web API modules, and collection/object helpers
• Bandit clock application startup fixed for --no-start test runs
• shared runtime/context message handling fixed for context state without :mode

Audit and benchmark tooling

• bench/vm_compiler_compat.exs
• bench/vm_compiler_corpus.exs
• bench/vm_compiler_opcode_coverage.exs
• bench/vm_compiler_perf.exs
• bench/vm_compiler_semantic_gaps.exs
• bench/vm_compiler_test262.exs
• test/support/vm_compiler_audit.ex
• compiler acceptance and auto-mode tests

Current compiler audit status

• QuickJS bytecode opcode coverage: 245 / 246 unique opcodes
  • remaining missing opcode: invalid, intentionally unsupported
• strict compiler Test262 statement window: 1582 / 1582 passing
• semantic compiler corpus: 1000 / 1000 compiled with zero mismatches, fallbacks, or crashes
• compiler invoke perf improved from 45.239µs to 42.845µs
• current compiler perf audit average speedup: 1.113x

Recent validation

• mix compile --warnings-as-errors
• mix lint
• mix dialyzer
• mix test test/js/parser test/vm/auto_mode_test.exs test/vm/compiler_differential_test.exs test/web_apis/beam_fetch_test.exs test/web_apis/beam_text_encoding_test.exs test/web_apis/beam_buffer_test.exs test/web_apis/beam_streams_test.exs test/web_apis/event_source_test.exs
• mix test --no-start --exclude napi_addon --exclude napi_sqlite test/web_apis/event_source_test.exs test/web_apis/beam_event_source_test.exs
• PARSER_BENCH=vm_compiler_semantics ./autoresearch.sh
• TEST262_LIMIT=1500 TEST262_CASE_TIMEOUT=5000 PARSER_BENCH=vm_compiler_test262 ./autoresearch.sh

Previous broad validation:

• QUICKBEAM_BUILD=1 MIX_ENV=test mix test
• MIX_ENV=test QUICKBEAM_BUILD=1 mix test test/vm/js_engine_test.exs --include js_engine --seed 0
• mix format --check-formatted
• mix credo --strict
• mix dialyzer
• mix ex_dna
• zlint lib/quickbeam/*.zig lib/quickbeam/napi/*.zig
• bunx oxlint -c oxlint.json --type-aware --type-check priv/ts/
• bunx jscpd lib/quickbeam/*.zig priv/ts/*.ts --min-tokens 50 --threshold 0