copybook-safe-ops

Panic-safe conversion and arithmetic helpers extracted from copybook-utils.

This crate owns narrowly scoped helpers that keep operations fallible:

• parsing numeric text into integers,
• checked division and array-bound arithmetic,
• checked numeric narrowing conversions,
• checked string and slice access helpers,
• safe string write utilities.

Division and slice access helpers are delegated to copybook-safe-index. Text-oriented parsing/write helpers (parse_*, safe_parse_*, safe_string_char_at, safe_write*) are delegated to copybook-safe-text.

All helpers return copybook_error::Result with explicit copybook-error codes and are intended for internal copybook-rs crates where panic-free execution is required.