Emitting raw terminal control sequences

Warns when echo or printf emits a raw terminal control sequence — the escape introducer \x1b, \033 or \e followed by [ (a CSI: cursor moves, screen clears, colour) or ] (an OSC: ]0; sets the window title, ]8;; plants a clickable hyperlink). Rendered into a terminal, log or IDE that does not neutralise them, these forge what a human reads back. This is a broad warn on purpose: a colourised build line trips it too, and that is an acceptable cost for a warning. Because its own trigger is an echo/printf, the echo quoted-MENTION carrier is NOT exempt here — an echo that prints an escape is exactly the case — while a search, a git commit -m message and a curl --data body that only name one are left alone. Matches the escape written as a backslash sequence in the command text. MISSES a raw ESC byte pasted literally, a sequence printed by a compiled program or a script file rather than an inline echo/printf, and tput, which reads terminfo and emits nothing literal in the command. The exemption holds only while every shell metacharacter stays inside the quotes.