Codegen: `const` + `var` in same function panics with duplicate variable

[mjm918]

Description

Declaring a const followed by a var in the same function causes a Cranelift panic: the variable var0 has been declared multiple times.

Steps to Reproduce

fn main() {
    const axx: int = 2;
    var x: int = 10;
}

Expected: Compiles and runs
Actual: Panic: the variable var0 has been declared multiple times

Root Cause

In namlc/src/codegen/cranelift/mod.rs:

• Statement::Var correctly uses Variable::new(ctx.var_counter) and increments ctx.var_counter (line 1721-1722)
• Statement::Const incorrectly uses Variable::new(ctx.variables.len()) and does NOT increment ctx.var_counter (line 2478)

When const is the first statement, variables.len() == 0 assigns Variable(0). Since var_counter is never incremented, the next var also gets Variable(0), causing the Cranelift panic.

Fix

Change Statement::Const to use ctx.var_counter and increment it, matching the Statement::Var pattern:

let var = Variable::new(ctx.var_counter);
ctx.var_counter += 1;