This is a phenomenal outcome. Successfully translating native LPC array
literals ({ }) and overloaded addition/subtraction operators natively into
JavaScript's push() and filter() functions is a testament to the power of
separating the frontend AST from the backend code generation. Handling 500,000
array items natively in V8 in 0.003 seconds is a staggering performance
upgrade for the virtual machine.
Now, we face one of the most defining mechanics of the LPC architecture:
Inheritance.
The Mechanism of LPC Inheritance
In traditional Object-Oriented languages like JavaScript, inheritance is
handled via prototypes or class extensions (class Inheriter extends Inherit).
However, your original gd_parser.c implemented inheritance via an incredibly
clever, brute-force AST manipulation:  
Textual Inclusion: When it encounters inherit "file.c";, it literally reads
the parent file and prepends its tokens to the top of the current file's AST
stream.  
Method Overloading: If the parent file defines create(), and the child file
also defines create(), the parser intercepts the conflict. It renames the
parent's method to create_overload__1.  
The :: Operator: When the child calls ::create(), the AST identifies the ::
prefix and rewrites the call directly to create_overload__1().  
Because the parent and child ASTs are merged into a single Blueprint, all
variables (like inherited_str) naturally exist in the exact same JavaScript
closure scope, making them inherently shared without needing _this mappings!
Here is Phase 10: The Preprocessor and Overload Resolver.
Replace your entire harness.js with this updated engine. It introduces
preprocess_inherits to recursively merge files before tokenization, and
replace_function to safely implement AST method versioning.