For v30: Fix base language preferred over regional variant in auto-detection 🌐

[FloPinguin]

Description:

When the browser reports a locale like de-DE, the language selector didn't find an exact match and fell through to candidate matching, where it picked de-CH (Swiss German) over de (German) because longer codes were sorted first.

This adds an early check: if the base language code (e.g. de) is directly supported, return it immediately before scanning regional candidates.

FYI @Aotumuri

Please complete the following:

• I have added screenshots for all UI updates
• I process any text displayed to the user through translateText() and I've added it to the en.json file
• I have added relevant tests to the test directory
• I confirm I have thoroughly tested these changes and take full responsibility for any bugs introduced

Please put your Discord username so you can be contacted if a bug or regression is found:

FloPinguin

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: cf097fcd-f090-4f9b-8971-d316214fb89e

📥 Commits

Reviewing files that changed from the base of the PR and between 2be8588 and 4b500e0.

📒 Files selected for processing (1)

• src/client/LangSelector.ts

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Walkthrough

The getClosestSupportedLang method now prioritizes immediate matches of language base codes (first two characters) within the supported language set, bypassing the previous candidate filtering and specificity sorting logic for base matches.

Changes

Cohort / File(s)	Summary
Language Fallback Resolution src/client/LangSelector.ts	Modified getClosestSupportedLang to return a language base code immediately upon finding an exact match in the supported set, rather than filtering candidates by prefix and sorting by length. Speeds up fallback resolution for inputs like xx-YY while preserving exact language match behavior.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

A language seeker finds its way,
Base codes now match without delay,
No sorting long, just swift and true,
The closest tongue for me and you! 🌍

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main fix: base language is now preferred over regional variants in auto-detection, which aligns with the changeset that modifies language fallback logic.
Description check	✅ Passed	The description is directly related to the changeset, providing clear context about the problem (longer regional codes picked before base language) and the solution (early base language check).
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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