Chat: collapse identical mirrored lines to (xN)

Card 5da196.

InfoText.AddLine mirrors every line unconditionally into the chat log — action spam (button mashing, blocked actions) flooded it with identical rows.

AddLog(Line, Priority, Collapse) opt-in: if FILE_Log[1] (same priority) is the same line, or that line with an existing (xN) suffix, the suffix is rewritten to (xN+1) in place and entry.Time refreshes (keeps the line alive under sustained spam vs the age-fade). Only the newest entry is ever touched — non-consecutive history is safe. InfoText.AddLine passes Collapse=true; user echo (> ...) and command outputs do not collapse.

10 identical warnings → warning (x10).

Verified: per-file luajit clean.