feat(wrap): add word wrapping mode

[NORMAL-EX]

Summary

Closes #3079

This PR adds a new word option to the --wrap argument that wraps text at word boundaries (spaces) instead of breaking in the middle of words.

Changes

1. wrapping.rs: Added Word variant to WrappingMode enum
2. clap_app.rs: Added word to the allowed values for --wrap
3. app.rs: Handle word option and map to WrappingMode::Word
4. printer.rs: Implemented word wrapping logic that:
   • Wraps at word boundaries (spaces) when possible
   • Falls back to character wrapping for words longer than the terminal width
   • Trims leading spaces after wrapping to avoid indentation issues
5. doc/short-help.txt and doc/long-help.txt: Updated help text

Usage

# Word wrapping
bat --wrap=word file.txt

# With terminal width
echo "Lorem ipsum dolor sit amet" | bat --wrap=word --terminal-width=20

Behavior

Mode	Description
auto	Default behavior (character wrap in non-interactive, no wrap in interactive)
never	No wrapping
character	Wrap at any character
word	Wrap at word boundaries, fall back to character wrap for long words