Terminal: consume non-CSI/OSC escapes (SS3 ESC O, charset ESC(, keypad) so stray 'B' stops leaking in tmux

[bedro96]

What to build

Escape sequences other than CSI (ESC [) and OSC (ESC ]) are not consumed by the terminal parser, so their trailing bytes leak as visible text. Confirmed on the Android emulator against a live SSH shell running tmux:

• The prompt/status render stray Bs: sshtest@kukovmB:~B$, tmux status ... 03-Jul-2B.
• Controlled probe results:
  • printf 'ss3_down:[\033OBx]\n' -> renders ss3_down:[Bx] (the SS3 ESC O B leaked its B; no cursor move)
  • The persistent prompt Bs match ESC ( B (designate ASCII/G0), which tmux and many apps emit constantly.

Root cause: the parser handles ESC [ and ESC ] but treats other escape introducers as text. It must recognize and consume the standard escape families:

• SS3: ESC O <final> (e.g. ESC O B) — consume introducer + one final byte.
• Charset designation: ESC ( <x>, ESC ) <x>, ESC * <x>, ESC + <x> — consume intermediate + one final.
• Two-char escapes: ESC =, ESC > (keypad), ESC 7, ESC 8, ESC D, ESC M, ESC E, ESC c, etc. — consume without leaking.
• Anything unrecognized after ESC should be consumed conservatively (not printed).

Verified GOOD and must NOT regress (all correct on the emulator): CSI cursor motion — ESC[B (down), ESC[3C (forward), ESC[1A (up) with overwrite (up_over -> upOVERr:L1); ls -al, du -sh .; 256-color/bold; in-place spinner; OSC title/color already swallowed; no 0; leak.

Acceptance criteria

• ESC O B (and other SS3 finals) produce NO visible text and are treated as the corresponding control (or no-op), not printed.
• ESC ( B / ESC ) 0 and other charset-designation sequences are fully consumed (no stray B/0).
• ESC =, ESC >, ESC 7/8, ESC D/M/E/c are consumed without leaking.
• In tmux over SSH, the prompt and status bar render with NO stray B characters.
• Handling is correct across chunk-split boundaries.
• Existing CSI cursor motion, SGR colors, OSC handling, ls -al/du output remain correct (regression-covered).
• Unit tests cover each escape family above using the exact probe fragments; ./run-tests.sh green.

Blocked by

None - can start immediately.

Agent workflow

Work test-first (/tdd): add failing tests for ESC O B, ESC ( B, and the two-char escapes leaking text, then implement consumption in the parser, and iterate (/fleet) until tmux shows no stray characters and ./run-tests.sh is green. Do not release/build the APK from untested code. Note: final on-device sign-off is done on the Android emulator running tmux.