Canonical form for chat filter matching.

Blocklist entries and incoming messages both go through normalize/1, so a word stored as "idiot" still matches "ïd１0T" and "iiiidiot". The transform is deliberately lossy and identical on both sides — it is a matching key, never something to show a player.

Steps, in order: lower-case; decompose and drop diacritics; drop zero-width and soft-hyphen characters; map common leetspeak substitutions; drop everything that is not a letter, digit or space; collapse runs of a repeated character to one; collapse runs of whitespace to one.

Known gap: letters spaced out individually ("i d i o t") survive as separate tokens and do not match. Catching those means matching across word boundaries, which turns benign phrases into hits far more often than it catches evasion.