Improve markdown linter and add pre-commit bypass

[bbbreaddd]

Markdown linter:

• Fix the a/an grammar check (it missed words starting with g, h, j) lint-markdown a/an check misses consonants g, h, j in Check 12 #5711 and stop it wrongly flagging cases like "an hour", "a European", and "an m3u"
• Ignore the posts/, other/, and public/ folders, and skip non-file paths
• Only use colors in a real terminal, so captured logs (VS Code, CI) no longer show raw color codes like [36m
• Underline the exact part of the line that has the problem, making issues easier to spot

Pre-commit hook:

• When a check fails in a terminal, ask whether to commit anyway; when not interactive (IDE/CI), show how to bypass with git commit --no-verify
• Quiet down lint-staged's output so failures are cleaner to read

[bbbreaddd]

and improved the message that shows up when Prettier fails as well