Implement Local Variables and Closures

Add local variables and closure support to your VM in C.

Requirements:

• Ensure STORE_LOCAL idx and LOAD_LOCAL idx work correctly in call frames
• Add OP_CLOSURE opcode that creates a closure object with a code address and upvalue count
• Add OP_LOAD_UPVALUE idx and OP_STORE_UPVALUE idx opcodes
• Define a Closure struct with code_address, upvalue_count, and upvalues array
• When OP_CLOSURE executes, capture the specified number of values from the stack as upvalues
• Demonstrate a closure that captures an outer variable and uses it after the outer function returns
• Print the closure creation, upvalue capture, and each upvalue access
• Show that the captured value persists even after the outer frame is popped

Test:

• Show local variable storage and retrieval
• Show closure creation capturing outer variables
• Show upvalue access inside closure execution
• Show STORE_LOCAL modifying a local variable