## Problem
The Arabic locale strings in `ar.json` use the Arabic comma `،` (U+060C)
as separator:
```json
"com.affine.calendar-date-picker.week-days": "أ،إث،ث،أر،خ،ج،س"
```
But `day-picker.tsx` splits on ASCII comma only — causing all
weekday/month names to render as a single unsplit string in Arabic
locale.
## Fix
Change `.split(',')` to `.split(/[,،]/)` in two call sites — matches
both ASCII and Arabic comma.
## Impact
One-line fix per call site. No other functionality affected. All
non-Arabic locales unchanged.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* Date picker rendering updated to correctly handle both ASCII and
Arabic/Persian comma formats when determining month and weekday labels.
This fixes inconsistent header and month-name displays in locales using
different comma characters while preserving existing interactions and
behavior.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
## Changes
### RTL Support (automatic, locale-driven)
- Add `rtl?: boolean` metadata to locale definitions in
`SUPPORTED_LANGUAGES`
- Set `rtl: true` for Arabic (`ar`), Persian (`fa`), and Urdu (`ur`)
- Automatically set `document.documentElement.dir` based on locale RTL
metadata on language change
- Remove hardcoded `lang="en"` from HTML template — JS now controls both
`lang` and `dir`
### Arabic Translations
- Add 100 missing keys to `ar.json` (Calendar integration, Doc
Analytics, MCP Server, AI Chat, and more)
- Arabic locale now has 2,313/2,313 keys (100% coverage, matches
`en.json` exactly)
## Testing
Switching to Arabic/Persian/Urdu now automatically flips the entire UI
layout to RTL without any manual feature flag.
Fixes#7099
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Added Right-to-Left (RTL) support for Arabic, Persian, and Urdu with
automatic document direction and language attributes when a language is
selected.
* **Refactor**
* Centralized and reordered internal language handling so document
language and direction are applied earlier and consistently.
* **Chore**
* Set a default text direction attribute on the base HTML template.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Mohad