Script-scoped non-strict assignment and delete

Date: 2026-05-15 Area: engine Pull Request: #645

Tightened --compat-non-strict-mode to Script-source semantics and completed the assignment/delete behavior required by #586. Failed ordinary object/global writes now silently preserve the assigned expression value only in non-strict Script mode, identifier delete can remove configurable global object properties, modules ignore the compatibility flag for strict this/arguments/parser/compiler decisions, bytecode format v31 adds loose set/global-delete opcodes, and the test262 runner now passes the flag only to non-onlyStrict Script tests. language.md. language.md. bytecode-vm.md. test262.md.