Add JavaScript S-expression execution engine

[rogeralsing]

Summary

• add the Asynkron.JsEngine library that lexes JavaScript into S-expressions and evaluates them with Lisp-like semantics
• expose a JsEngine facade, cons cell primitives, and environments with documentation updates
• create Asynkron.JsEngine.Tests to validate parsing, evaluation, closures, and host interop

Testing

• dotnet build Asynkron.OTelMCP.sln
• dotnet test Asynkron.OTelMCP.sln

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https://chatgpt.com/codex/tasks/task_e_690d1332a964832893299aeb69ca57f3

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Note

Introduces Asynkron.JsEngine to parse JavaScript into S-expressions and evaluate with JS-like semantics, plus comprehensive tests and solution/docs wiring.

• New library src/Asynkron.JsEngine:
  • Core runtime: Lexer, Parser -> S-expressions (Cons, Symbol, JsSymbols); Evaluator with lexical Environment and control signals.
  • Language features: variables (let/var/const), functions/closures, object/array literals (JsObject/JsArray), property/index ops, new, classes with extends/super, control flow (if/for/while/do-while/switch/try-catch-finally), logical/equality operators; host interop via HostFunction; public JsEngine façade.
• Tests tests/Asynkron.JsEngine.Tests: xUnit coverage for parsing, evaluation, closures, interop, arrays/objects, classes/inheritance, control flow, operators.
• Solution/Docs: add projects to Asynkron.OTelMCP.sln; update src/context.md; add Asynkron.JsEngine/context.md and tests context.

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Bug: Floating-Point Zero-Check Fails Near-Zero Values

Division by zero check compares floating-point ToNumber(right) using exact equality with 0, which can fail due to floating-point precision issues. Values very close to zero but not exactly zero may incorrectly pass the check, while the division itself could still produce infinity or unexpected results.

 

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Bug: Arithmetic division by zero throws exception instead of Infinity

Division by zero throws DivideByZeroException instead of returning Infinity like JavaScript. In JavaScript, dividing by zero produces Infinity or -Infinity, not an exception. This breaks JavaScript semantics and will cause runtime errors for valid JavaScript code like 1/0.

 

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Bug: Redundant Dictionary Update After SetPrototype Call

SetProperty always sets the dictionary entry on line 49 even after calling SetPrototype for __proto__. Since SetPrototype already updates the dictionary, this redundantly overwrites the same value. The method needs a return after line 46 or an else clause to avoid the redundant assignment.