Clean 17 prompts (grammar/spacing/register/\n) + shorten README, cite M-IFEval only

Fix 6 scoring-affecting prompts: end_phrase mismatch (145), off-by-one moins de (154/178/210/219), untranslated EN (62), accent key (204)

Add French IFEval (M-IFEval) in google/IFEval format

initial commit