fix: mark .husky/pre-commit executable

.husky/pre-commit was committed with mode 100644 back in rpamis#106, so git
silently skips it on every fresh clone/checkout regardless of platform
or editor (git only runs a hooksPath script if its executable bit is
set). This has been silently disabling the format:check/lint-staged
pre-commit automation described in CLAUDE.md for all contributors since
that commit. Verified the hook actually runs lint-staged after chmod +x.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: 1919chichi