Feature request: proper RTL support for Persian and Arabic

[Shahzad55]

"Disrupted user interface layout in right-to-left (RTL) languages ​​(Persian/Arabic)."
Responses and text appear disorganized in the right-to-left mode, and the page alignment and layout are not optimized.

[Shahzad55]

[aturzone]

I took the core half of this request: the locale registry is where RTL has to start, because the package reference documents that it supplies <html lang> but not bidirectional layout (packages/client/locale/README.md, Known Limitations). Branch and commit:

https://github.com/aturzone/deepseek-harness/tree/feat/locale-writing-direction (eaf80faca4)

What the change does

• LanguageRegistration/LocaleDefinition gain an optional direction: 'ltr' | 'rtl' (omitted = ltr; shipped languages stay LTR).
• The runtime points <html dir> at the active language and reasserts it when a language pack loads, unloads, or the selection changes. Direction lives on the definition rather than the snapshot, so existing snapshot consumers are untouched.
• Invalid directions are rejected at registration (language packs are plain JavaScript, so this is a real untrusted boundary; the check carries a narrow lint exception with that reason).
• Tests cover shipped LTR, an RTL pack switching both ways, unload fallback, and rejected directions; locale tests 72/72, client/locale/src 100% coverage, typecheck 5/5, full lint 0 errors. README pairs updated.

What this does not do, deliberately. Converting the GUI to RTL layout is per-component work: 652 physical CSS declarations across 141 files (left/right, margin-left/right, text-align: left/right, radii, gradients). The registry should not paper over that with a global flip; each component must move to logical properties (inset-inline-start, margin-inline, text-align: start, border-start-*-radius, …) and its own snapshot/visual evidence. This change gives language packs the declaration and document attribute they were missing, which is the prerequisite for those follow-ups.

Context in the tracker: this thread is the umbrella request; #11672/#7404/#8935 are ecosystem packs that already implement per-paragraph or per-block RTL as plugins. Once this core attribute exists they can declare direction: 'rtl' instead of guessing, and #11248 (mixed Arabic/Latin rendering order) remains a separate bidi-text issue rather than layout direction.

The repository closes PRs, so the branch is the deliverable; happy to reshape it (per-snapshot direction, per-package CSS slices) if maintainers prefer a different first step.