feat(tui): RTL/Bidi support for Persian, Arabic, Hebrew, and Urdu text

[liuhao1024]

Summary

Implements Phase 1 (MVP) of RTL/Bidi support in the Hermes TUI, making Persian, Arabic, Hebrew, and Urdu text render correctly for ~500M+ potential users.

Problem

Persian, Arabic, Hebrew, and Urdu text renders left-aligned with disconnected letters in the Hermes TUI (hermes --tui). This makes the TUI unusable for RTL language users.

Changes

ui-tui/src/lib/text.ts

• Added isRtl() function using the first-strong-character heuristic (matches CSS direction: auto behavior)
• Detects RTL scripts via Unicode code point ranges: Hebrew (0590-05FF), Arabic/Persian (0600-06FF), Arabic Supplement (0750-077F), Arabic Extended-A (08A0-08FF), Arabic Presentation Forms (FB50-FDFF, FE70-FEFF)
• Strips ANSI escape codes before direction detection

ui-tui/src/components/messageLine.tsx

• Applies flexDirection="row-reverse" for RTL messages (gutter moves to right side)
• Applies alignItems="flex-end" for RTL message content (right-aligned)
• Omits fromLeftEdge for RTL messages (selection zone follows reversed layout)

ui-tui/src/__tests__/text.test.ts

• 10 new unit tests covering: empty string, English (LTR), Chinese (LTR), Persian, Arabic, Hebrew, Urdu, leading whitespace handling, LTR-first mixed text, ANSI stripping

Testing

All existing tests continue to pass. No new dependencies.

Closes #41454

[tonydwb]

Code Review Summary

Verdict: Approved

RTL/Bidi support for Persian, Arabic, Hebrew, Urdu — well-scoped, no elsewhere surface area.

Highlights

• isRtl first-strong-char detection matches CSS direction: auto semantics, which is what users expect.
• Row flex-direction (row-reverse vs row) and fromLeftEdge are flipped by the rtl flag — visual layout inverts correctly for RTL.

The change is purely additive in the desktop UI; no gateway or server-side impact.

No issues.

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Reviewed by Hermes Agent

[teknium1]

Thanks for the focused TUI RTL contribution. Current main now performs software bidi reordering in ui-tui/packages/hermes-ink/src/ink/bidi.ts:55-110, but MessageLine still lays out the gutter and body left-to-right (ui-tui/src/components/messageLine.tsx:229-237), so the alignment portion remains useful.

Problems

• ui-tui/src/lib/text.ts:382 returns on the first non-whitespace code point, not the first strong directional character. Leading punctuation such as (مرحبا) is therefore classified LTR.
• ui-tui/src/components/messageLine.tsx:244 uses alignItems on a default row Box. That aligns the vertical cross-axis, not horizontal body placement; RTL text remains left-aligned inside its body box. Use a main-axis layout property and cover it with a rendered transcript assertion.
• The response separator at ui-tui/src/components/messageLine.tsx:220-228 remains left-oriented when an RTL assistant message shows details.

Suggested changes

• Make detection skip neutral characters until a strong RTL/LTR character and add punctuation/numeric-prefix fixtures.
• Add renderSync coverage alongside ui-tui/src/__tests__/messages.test.ts:31-72 for RTL gutter/body/separator placement.

Automated hermes-sweeper review.

[teknium1]

This returns for the first non-whitespace character, not the first strong directional character. (مرحبا) and 1. مرحبا therefore classify as LTR. Skip bidi-neutral characters until an RTL or LTR strong character, and add fixtures for those prefixes.

[teknium1]

The inner Box defaults to flexDirection: 'row', so alignItems controls its vertical cross-axis rather than horizontal text placement. RTL content will remain left-aligned in this fixed-width body Box; use the appropriate main-axis alignment and add a rendered layout assertion.