Unskip CSI/OSC sequences that are safely ignored or no-op in xterm.js
using assertNoModeChange, following the pattern from prior commits.
Add window option integration tests for GetWinSizeChars (18t) and
PushTitle/PopTitle (22t/23t).
Keep skipped: XTHIMOUSE (parsed as scroll down), DECSLRM (parsed as
SCOSC), DECGPCS/DECGRPM aliases (covered by mode 45/47 tests), and
addon-only graphics sequences.
Co-authored-by: Daniel Imms <Tyriar@users.noreply.github.com>