Admit derived this after super

[rogeralsing]

Summary

• allow derived constructor production-bytecode plan shapes to use this after a super(...) boundary
• make sync VM LoadThis resolve the current environment this binding and throw the existing derived-constructor ReferenceError when it is still uninitialized
• flip the super(); this.value = value runtime proof to require a production route hit and update constructor route docs

Verification

• rtk dotnet test tests/Asynkron.JsEngine.Tests -c Release --filter 'FullyQualifiedName~UnifiedBytecodeProductionEligibilityTests.Evaluate_DerivedThisAssignmentAfterSuper_AcceptsOwnedPropertyWrite'
• rtk dotnet test tests/Asynkron.JsEngine.Tests -c Release --filter 'FullyQualifiedNameUnifiedBytecodeProductionEligibilityTests.Evaluate_DerivedThisAssignmentAfterSuper_AcceptsOwnedPropertyWrite|FullyQualifiedNameUnifiedBytecodeProductionConstructCallTests.SuperConstructThenThisAssignment_UsesProductionFastPath|FullyQualifiedNameUnifiedBytecodeProductionConstructCallTests.SuperConstruct_InitializesThis|FullyQualifiedNameUnifiedBytecodeProductionConstructCallTests.SuperConstructWithSpread_UsesProductionFastPath|FullyQualifiedNameUnifiedBytecodeProductionConstructCallTests.DerivedConstructorWithInstanceField_UsesProductionFastPathAndInitializesAfterSuper|FullyQualifiedNameClassSuperSemanticsTests'
• rtk dotnet test tests/Asynkron.JsEngine.Tests -c Release --filter 'FullyQualifiedNameUnifiedBytecodeProductionEligibilityTests|FullyQualifiedNameUnifiedBytecodeProductionInvocationTests|FullyQualifiedNameUnifiedBytecodeProductionSpreadCallTests|FullyQualifiedNameUnifiedBytecodeProductionConstructCallTests|FullyQualifiedNameExpressionProgramLoweringTests|FullyQualifiedNameExpressionProgramCoverageMapTests|FullyQualifiedName~AstFreeExecutionAssertionTests'
• rtk dotnet build src/Asynkron.JsEngine/Asynkron.JsEngine.csproj -c Release
• rtk rg 'EvaluateExpression(|ProfileEvaluateExpression(' src/Asynkron.JsEngine/Ast/TypedAstEvaluator.ExecutionPlanRunner*
• rtk rg -n 'SuperConstructThenThisAssignment_Declines|without .*this|this body reads/writes|ClassConstructorActivation.*without|LoadThis.*return false' docs/unified-bytecode-expansion-contract.md tests/Asynkron.JsEngine.Tests/UnifiedBytecodeProductionConstructCallTests.cs tests/Asynkron.JsEngine.Tests/UnifiedBytecodeProductionEligibilityTests.cs src/Asynkron.JsEngine/Ast/TypedAstEvaluator.SyncFunctionInvoker.cs
• rtk git diff --check

Roslynator/cosmetic gates intentionally skipped per maintainer direction to get bytecode route code in.

[Copilot]

Pull request overview

This PR updates the unified-bytecode “production fast path” for derived class constructors so that this can be safely read/written after the super() boundary, matching ES derived-constructor semantics while keeping execution on the production VM route.

Changes:

• Expands derived-constructor production eligibility to allow post-super() this usage (e.g., this.value = ...) and updates related expectations.
• Updates the unified-bytecode VM LoadThis opcode to resolve this from the current environment binding and to throw the existing derived-constructor ReferenceError when this is still uninitialized.
• Adjusts tests and contract docs to reflect that the derived-constructor route now uses the production fast path for super(); this... patterns.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/Asynkron.JsEngine.Tests/UnifiedBytecodeProductionEligibilityTests.cs	Adds eligibility coverage for derived constructors writing to this after super().
tests/Asynkron.JsEngine.Tests/UnifiedBytecodeProductionConstructCallTests.cs	Updates a constructor test to assert the production fast path is used after super(); this....
src/Asynkron.JsEngine/Execution/UnifiedBytecode/UnifiedBytecodeVirtualMachine.cs	Changes LoadThis to resolve this via environment binding and throw on uninitialized derived-constructor this.
src/Asynkron.JsEngine/Ast/TypedAstEvaluator.SyncFunctionInvoker.cs	Updates derived-constructor production plan-shape scan to permit LoadThis.
docs/unified-bytecode-expansion-contract.md	Updates documentation to reflect the admitted derived-constructor this usage after super().

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