Improve word splitting for string normalization

[mworrell]

No description provided.

[Copilot]

Pull Request Overview

This PR improves the word splitting logic in string normalization to better handle various Unicode space and control characters. The changes refactor separator detection into three distinct macros and enhance the normalize_words functions to properly handle characters that should be ignored versus those that should split or be mapped to spaces.

Key changes:

• Introduces three new character classification macros: is_sep, is_map_space, and is_word_ignore_char for more granular control over character handling
• Updates normalize_words_word and normalize_words_sep functions to use the new macros for improved word boundary detection
• Adds test coverage for multi-word normalization scenarios

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/z_string_normalize.erl	Refactors character classification into dedicated macros and updates word splitting logic to handle separators, space-like characters, and ignorable characters distinctly
test/z_string_test.erl	Renames existing single-word test and adds new multi-word normalization test case to verify improved word splitting behavior

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