Add terminal-escapes.js with a canonical clear sequence (home, CSI 3J/2J,
SGR reset) and use it for fish ^L and fish-tty-repro. Match /bin/clear in
coreutils with the same sequence and a sync comment. Harden fish-readline
for bracketed paste, SS3/legacy CSI arrows, focus CSI, and common ~ keys;
widen stripAnsi CSI matching. Add brittle and coreutils tests for the
sequence and paste/focus/^L behavior.
