Add boundary checks in gen_associated_data_from_range()

[Copilot]

gen_associated_data_from_range() performed unchecked u32 arithmetic on user-supplied CLI values: end - start underflows when end < start, and end - start + 1 overflows when end == u32::MAX && start == 0.

Changes

• Input validation: Return CMDToolError early when end < start
• Checked arithmetic: Replace end - start + 1 with (end - start).checked_add(1), returning an error on overflow
• Tests: Add test_gen_associated_data_from_range_end_less_than_start and test_gen_associated_data_from_range_max_overflow

// Before (panics/wraps on bad input)
let num_ints = end - start + 1;

// After
if end < start {
    return Err(CMDToolError {
        details: format!("invalid range: end ({end}) must be greater than or equal to start ({start})"),
    });
}
let num_ints = (end - start).checked_add(1).ok_or_else(|| CMDToolError {
    details: format!("range [{start}, {end}] is too large: count overflows u32"),
})?;

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add boundary checks in gen_associated_data_from_range()</issue_title>
<issue_description>> Since start/end are user-provided (via the CLI wrapper), this function should defensively validate end >= start and avoid unchecked u32 arithmetic (currently end - start + 1 will overflow/panic when end < start, and can also overflow when end == u32::MAX && start == 0). Consider returning an error on invalid ranges and computing the count with checked arithmetic.

Originally posted by @copilot in #763</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add boundary checks in gen_associated_data_from_range() #788

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