Admit implicit arguments object reads

[rogeralsing]

Summary

• Admit bounded implicit arguments object reads through production unified bytecode.
• Compile implicit arguments loads as environment-backed dynamic identifier loads so the existing activation environment materializes the arguments object.
• Extend the first-boundary computed read path for arguments[index] while keeping arguments update and call forms declined.

Verification

• rtk dotnet test tests/Asynkron.JsEngine.Tests -c Release --filter 'FullyQualifiedNameUnifiedBytecodeProductionEligibilityTests.Evaluate_ArgumentsAccess_AcceptsImplicitArgumentsObjectRead|FullyQualifiedNameUnifiedBytecodeProductionEligibilityTests.Evaluate_TypeOfImplicitArgumentsObject_AcceptsLiteralObjectType|FullyQualifiedNameUnifiedBytecodeProductionEligibilityTests.Evaluate_UpdateImplicitArgumentsObject_DeclinesWithDynamicLookupDependency|FullyQualifiedNameUnifiedBytecodeProductionEligibilityTests.Evaluate_CallImplicitArgumentsObject_DeclinesWithArgumentsDependency|FullyQualifiedNameUnifiedBytecodeProductionInvocationTests.ImplicitArgumentsObjectRead_UsesUnifiedBytecodeProductionFastPath|FullyQualifiedNameUnifiedBytecodeProductionInvocationTests.TypeOfImplicitArgumentsObject_UsesUnifiedBytecodeProductionFastPath|FullyQualifiedName~UnifiedBytecodeProductionInvocationTests.UpdateImplicitArgumentsObject_DeclinesAndFallsBack'
• 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 git diff --check

[Copilot]

Pull request overview

This PR expands production unified-bytecode routing to admit read-only uses of the implicit arguments object (e.g., arguments[0]) by compiling those loads as environment-backed dynamic identifier reads, and by extending the first-boundary computed read candidate logic accordingly.

Changes:

• Update unified-bytecode production eligibility to allow implicit arguments identifier reads when ordinary dynamic identifier environment operations are permitted.
• Extend the computed property read “first boundary” compilation/eligibility path to treat implicit arguments reads as valid bases (compiled via LoadDynamicIdentifier).
• Update tests and the expansion contract documentation to reflect that implicit arguments reads now take the unified-bytecode production fast path.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/Asynkron.JsEngine.Tests/UnifiedBytecodeProductionInvocationTests.cs	Updates invocation test to assert implicit arguments[0] uses the production fast path.
tests/Asynkron.JsEngine.Tests/UnifiedBytecodeProductionEligibilityTests.cs	Updates eligibility test to accept implicit arguments read and assert dynamic identifier load is present.
src/Asynkron.JsEngine/Execution/UnifiedBytecode/UnifiedBytecodeProductionEligibility.cs	Broadens eligibility scanning/candidate detection to permit implicit arguments reads under allowed dynamic identifier operations.
src/Asynkron.JsEngine/Execution/UnifiedBytecode/UnifiedBytecodeCompiler.cs	Allows compiling implicit arguments loads (as dynamic identifier loads) and wires this into first-boundary computed reads.
src/Asynkron.JsEngine/Ast/TypedAstEvaluator.SyncFunctionInvoker.cs	Reworks activation gating to enable the new implicit arguments read path.
docs/unified-bytecode-expansion-contract.md	Updates the eligibility/contract ledger to reflect the new admitted arguments read behavior.

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