- Use the flag-aware implementation for both make and make bonus
(bonus/ moved to src/, _bonus suffix dropped, bonus rule = all)
- Do not treat zero-length output (%s with "", %.0d with 0) as an error
- Return -1 without printing when a % has no conversion ("abc%", "%5")
- Keep field width with '#', '+' and ' '; ignore '0' with '-'
- Fix '#' prefix on zero, '+'/' ' with zero padding, INT_MIN negation UB
- Add README.md required by the subject
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
