macOS uses U+202F (Narrow No-Break Space) in screenshot filenames
between the time and am/pm. When users type or paste these paths,
they use regular spaces, causing file-not-found errors.
Changes:
- Add resolve_path_with_unicode_fallback() to try U+202F variants
- Add resolve_paths_in_shell_command() for shell command paths
- Apply fix to read_file, read_image, and shell tools
- Fix read_image prompt docs: file_path -> file_paths (array)
- Add 6 unit tests for Unicode space normalization