fix(interpreter): prevent brace step overflow

[chaliy]

Motivation

• Prevent DoS and non-terminating brace expansions where large or specially-crafted ..step values could overflow or leave the loop unadvanced, bypassing the existing range-size cap and causing panics or unbounded resource growth.

Description

• Use i128 arithmetic for numeric brace range stepping by converting the step magnitude to i128 and iterating i and end as i128 so valid large i64 steps cannot overflow during iteration.
• Preserve the precomputed range-size cap (MAX_BRACE_RANGE) and the existing validation logic that rejects zero or non-numeric steps.
• Add a regression unit test test_try_expand_range_numeric_large_step_does_not_overflow that asserts correct behavior for ascending and descending large-step numeric ranges near i64 bounds.
• Modified file: crates/bashkit/src/interpreter/mod.rs.

Testing

• Ran cargo fmt --check and it passed.
• Ran cargo test -p bashkit test_try_expand_range_numeric_large_step_does_not_overflow --lib and it passed.
• Ran cargo test -p bashkit test_try_expand_range_alpha_large_step_does_not_loop --lib and it passed.

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	bashkit	b4eb923	Commit Preview URL	Jun 02 2026, 09:27 AM