fix(tui): strip ANSI from input buffer after gateway pipe break (#28419)

[Jiahui-Gu]

Summary

Fixes #28419. When the TUI gateway pipe breaks and the gateway auto-restarts, render bytes from stdout can leak into stdin. The composer's TextInput previously stripped only bracketed-paste markers (ESC[200~ / ESC[201~), so anything between them — including chunked / de-escaped CSI sequences like 35;104;62m — slipped through PRINTABLE and ended up in the input field, producing the characteristic ANSI flood reported in the issue.

Fix

ui-tui/src/components/textInput.tsx:

• New exported stripAnsiSequences() helper that strips full CSI / OSC / SS3 / two-byte-ESC / bare-ESC / C0+C1 control bytes.
• When residue still shows the orphan-CSI-flood signature (multiple \d+;\d+;\d+[A-Za-z] chains), an iterative cleanup pass removes leftover digits, ;, and stray CSI final letters. Ordinary user text (a; b; c, color: red;, 12;34) is preserved because the aggressive pass only fires when the orphan-flood signature is present.
• Applied at three paste-like input sites: the bracketed-paste branch in useInput, flushPaste(), and pastePlainText().

Test plan

• ui-tui/src/__tests__/textInputAnsiStrip.test.ts — 8 cases including the exact garbage shape from the bug report (102;71M5;104;62M... → \"\"), bracketed-paste-wrapped ANSI leaks, unicode/punctuation preservation
• vitest run shows no new regressions (2 pre-existing failures cursorDriftRegression, ink-resize also fail on main)
• tsc --noEmit clean

🤖 Generated with Claude Code

[Jiahui-Gu]

FYI for maintainer triage: noticed there's another open PR #28463 (fix(tui): recover degraded focus burst input) also targeting #28419, but with a different fix approach.

This PR specifically strips ANSI sequences from the input buffer (stripAnsiSequences() helper in textInput.tsx) to handle the chunked/de-escaped CSI sequences that leak through when the gateway pipe breaks and restarts. If #28463 already covers the input-buffer ANSI leak, happy to close. Different root cause angles may converge to the same fix — flagging so reviewers can pick whichever shape they prefer.

[teknium1]

Closing as redundant against current main.

This is part of the TUI/CLI ANSI/SGR/escape-leak cluster, most of which is already solved on main:

• In-buffer CPR/DSR + SGR mouse (esc / visible / bare) stripping lives in cli.py::_strip_leaked_terminal_responses_with_meta().
• SGR mouse-burst noise, fragment recovery, and X10 wheel-tail handling live in ui-tui/packages/hermes-ink/src/ink/parse-keypress.ts (shipped via fix(tui): swallow degraded mouse-burst noise so a stalled loop can't lock the composer #35512 and follow-ups).
• The exit-side leak (focus/mouse modes left enabled after Ctrl+C/SIGTERM leaking into the next shell) was just fixed in fix(cli): reset terminal input modes on TUI exit to stop focus/mouse leaks #36864.

Your work here overlapped this already-merged coverage. Thanks for the contribution and for helping surface the leak class — it's appreciated.