fix(tui): preserve Ctrl+J newline in VTE terminals

[rvdavid-rbi]

Summary

• preserve Ctrl+J as a newline chord in VTE-based terminals by detecting VTE_VERSION
• add regression coverage for Ubuntu/GNOME Terminal-style VTE environments
• keep the existing fallback behaviour for bare POSIX terminals with no terminal fingerprint

Fixes #51545.

Verification

• npm test -- --run src/__tests__/textInputPassThrough.test.ts
• npm run typecheck
• npm run build
• live TUI smoke test in a VTE-like env confirmed Ctrl+J renders a two-line composer input while Enter remains submit

[Copilot]

Pull request overview

Preserves Ctrl+J as a newline chord in VTE-based terminals (e.g., GNOME Terminal/Console) by extending the TUI composer’s terminal fingerprint detection, with a regression test to prevent the Ubuntu/VTE behavior from reappearing.

Changes:

• Detect VTE terminals via VTE_VERSION in shouldPreserveCtrlJNewline() to treat bare LF (\n) as an insert-newline chord rather than submit.
• Add a Vitest regression case covering a VTE-like environment (TERM=xterm-256color, VTE_VERSION set).
• Retain the existing “no fingerprint” fallback behavior (bare POSIX terminals keep Ctrl+J submitting).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
ui-tui/src/components/textInput.tsx	Adds VTE_VERSION fingerprint to preserve Ctrl+J newline handling.
ui-tui/src/tests/textInputPassThrough.test.ts	Adds regression coverage for VTE environments and keeps the bare-POSIX fallback test.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[rvdavid-rbi]

Thanks for the triage. To clarify scope: this PR fixes the TypeScript TUI renderer path in ui-tui/src/components/textInput.tsx, specifically shouldPreserveCtrlJNewline() and its Vitest coverage.

I saw the related PR #52102, which addresses the Python CLI predicate in cli.py. That appears to be the same root cause at a different layer rather than a direct duplicate.

Happy to do whichever maintainers prefer:

1. keep this PR focused on the TypeScript renderer layer,
2. expand this PR to also cover the Python CLI predicate, or
3. close this in favour of a combined maintainer-preferred patch.

My preference is to keep both layers covered, since VTE detection seems relevant in both input paths.

[teknium1]

Thanks for the focused TUI fix. Current main still lacks a VTE_VERSION branch in shouldPreserveCtrlJNewline() (ui-tui/src/components/textInput.tsx:128-150), while the composer sends bare-LF return events to the submit path unless that predicate is true (ui-tui/src/components/textInput.tsx:990-1000). The added predicate case and VTE regression test match that control flow.

The target files are unchanged from the PR's merge base through current HEAD (git diff --quiet 070ac2a71900f30b680ecafd4d68c162e9089a0a..HEAD -- ui-tui/src/components/textInput.tsx ui-tui/src/__tests__/textInputPassThrough.test.ts), so this remains a clean, focused salvage candidate. The related Python CLI path is separately addressed by #52102, consistent with the contributor's clarification.

Automated hermes-sweeper review.