[BUG] `len` function passes garbage value when evaluated as an argument.

[Melidee]

Describe the bug
When using the len function to take the length of an array as an argument to a function call, it passes an incorrect value in a format such as __length_1[@]. This behavior is not seen when assigning the result of len to a variable and then passing that variable to the function.

To Reproduce

import { printf } from "std/env"

fun print_length(length: Int) {
    echo(length)
}

// this prints the incorrect __length_1[@] text
let arr = ["a", "b"]
printf("Calling len function: ")
print_length(len(arr))

// this prints correctly
let arr_len = len(arr)
printf("Assigning len to a variable: ")
print_length(arr_len)

fun length_plus_one(length: Int): Int {
    // bash error: bad array subscript
    return length + 1
}

printf("Integer operation: ")
length_plus_one(len(arr))

This creates the output (on bash-4.3):

Calling len function: __length_2[@]
Assigning len to a variable: 2
Integer operation: bash: line 46: __length_6[@]: bad array subscript

This reproduces when compiling to all available targets (bash-4.3, bash-3.2, zsh, ksh). It's notable that while the value generated by len as a parameter is not a valid Int, it still type checks as a regular Int, which I verified with an if length is Int check. This behavior is also not seen from other function calls, including a wrapper function immediately returning len of a value.

Expected behavior
A len call passed as a parameter should be evaluated to a plain Int with a value which is only a single number and no extra labels or strings, and which can be used for int operations.

Additional context
Environment:

• MacOS Sequoia 15.6
• amber 0.6.0-alpha