ml-scan-set now checks ml-is-mutable-global? before adding set!/append!
targets to the needs-ref list. Previously, mutable globals like
*bind-tracking* got local `ref Nil` shadows that masked the global _ref,
causing `append!: expected list, got nil` in 43 bind-tracking tests.
Test runner: bind foreign registry functions (foreign-registered?,
foreign-lookup, foreign-names, foreign-register!, foreign-resolve-binding,
foreign-check-args, foreign-build-lambda) + initialize _cek_call_ref for
with-capabilities. 22/24 foreign tests now pass, 8 capabilities tests fixed.
Retranspiled sx_ref.ml — all mutable global shadows eliminated.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>