[cdrini]

Description

• The translate "To" language list now shows recently used languages (up to 3, saved in localStorage) in a "Recent" group at the top.
• The default "To" language is now the most recently used one, else the browser's language (if there's a model for it), else English.

Closes #1459

Technical

• Recent languages also stay in the full list; if localStorage is unavailable or invalid the list just shows without the group.
• Browser languages are matched exactly first, then by base language (e.g. fr-CA → fr, zh-CN → zh-Hans).

Testing

On the IA demo with the translate experiment enabled:

1. Choose a couple of "To" languages, reload: they show under "Recent" and the last one is preselected.
2. With no history (clear localStorage), set the browser language to e.g. French: "To" defaults to français. With an unsupported language (e.g. Icelandic) it defaults to English.

Screenshots/Videos

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 91.66667% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.03%. Comparing base (042a0e4) to head (7911500).

Files with missing lines	Patch %	Lines
src/plugins/translate/plugin.translate.js	91.66%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1619      +/-   ##
==========================================
+ Coverage   64.65%   65.03%   +0.38%     
==========================================
  Files          69       69              
  Lines        6309     6338      +29     
  Branches     1400     1409       +9     
==========================================
+ Hits         4079     4122      +43     
+ Misses       2190     2176      -14     
  Partials       40       40              

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