fix: i18n locale resolution (spurious es/fr 404s; short locales served English)

[kilbot]

What & why

Reported from production console: GET …/src/translations/es/wp-admin-landing-shared.json 404 (and fr, etc.).

Two bugs in the i18n config, confirmed by reproducing the actual network requests per locale:

1. Spurious 404 every load. i18next's default load: 'all' requested both the full locale es_ES (exists → 200) and the base language es (no such dir → 404). Page worked, but logged a 404 each load.
2. Short-locale users served English. A site whose WP locale is a language-only code (es, fr) requested only that → 404 → silent English fallback instead of the user's language.

Fix

• load: 'currentOnly' — request only the exact locale (our locale files are key-complete per lint-translations, so no region→base fallback layer is needed).
• loadPath is now a function that maps the requested code to an available directory via resolveLocaleDir (short es → es_ES, pt → pt_BR, zh → zh_CN; unknown → passthrough → 404 → bundled English).
• Extracted to a pure, unit-tested src/shared/locale-resolve.mjs (tests/locale-resolve.test.mjs).

Verified

Reproduced before/after with a headless harness — every locale now makes exactly one request to the correct dir; short codes resolve to their region; the es/fr 404s are gone.

Please review before merge — I'm not self-merging these.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Improved locale resolution to correctly handle exact language codes, hyphenated forms, and region variants with consistent directory selection.
• Performance
  • Optimized translation loading to request only the currently active locale, reducing extra companion requests.
• Tests
  • Added automated coverage for locale/region resolution behavior, including edge cases and unknown locale pass-through.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository: wcpos/coderabbit/.coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: c9dbb82d-6b1d-4cca-898d-3c35cc9bb58a

📥 Commits

Reviewing files that changed from the base of the PR and between 71363e5 and 0d61057.

📒 Files selected for processing (3)

• assets/js/welcome.js
• src/shared/locale-resolve.mjs
• tests/locale-resolve.test.mjs

🚧 Files skipped from review as they are similar to previous changes (1)

• src/shared/locale-resolve.mjs

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📝 Walkthrough

Walkthrough

Adds src/shared/locale-resolve.mjs exporting a LOCALE_DIRS allowlist and a resolveLocaleDir function that maps i18next locale codes to existing translation directory names. Updates i18n.ts to import and use this resolver as the HTTP backend loadPath function and sets load: 'currentOnly'. Adds a corresponding test file covering all resolution cases.

Changes

Locale resolver and i18n CDN path integration

Layer / File(s)	Summary
LOCALE_DIRS allowlist and resolveLocaleDir implementation src/shared/locale-resolve.mjs, tests/locale-resolve.test.mjs	New module exports LOCALE_DIRS (supported translation directory names) and resolveLocaleDir(lng) with exact-match, base-language, and passthrough logic. Tests cover full locale pass-through, short-code mapping, hyphenated inputs, region-variant preservation, unknown-locale passthrough, and an invariant that LOCALE_DIRS contains no short-code entries that would shadow region codes.
i18n backend wired to resolveLocaleDir src/shared/i18n.ts	Imports resolveLocaleDir, adds load: 'currentOnly' to suppress companion base-language loads, and replaces the Handlebars loadPath template with a function that calls resolveLocaleDir(lngs[0]) to compute the CDN URL for the correct locale directory.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🌐 A resolver steps in, tidy and bright,
No more guessing which folder's right.
es finds es_ES on the shelf,
Unknown codes just handle themselves.
CDN paths served without a fight! 🗂️

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title precisely summarizes the two primary bugs being fixed: spurious 404 errors on base language codes and short-locale users receiving English instead of their intended language.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/i18n-locale-resolution

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[chatgpt-codex-connector]

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Reviewed commit: 71363e543b

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[kilbot]

Fix triage

#	Source	File	Class	Category	Decision	Outcome
1	Codex	locale-resolve.mjs:31	Logic	P2 / Major	Fix	Hyphenated region codes (zh-TW, es-MX, pt-PT) resolved to the first region of the base language instead of the exact match. Normalizing -→_ and checking for an exact supported dir before the base fallback; adding the multi-region hyphen cases to the test (which would have caught it).
2	CodeRabbit	—	—	—	Skip	"No actionable comments 🎉"

Working through #1 now; will reply in-thread and push.

[kilbot]

✅ Fix round complete.

#	Source	Decision	Outcome
1	Codex locale-resolve.mjs:31	Fixed	0d61057 — normalize -→_, match exact region before base fallback (zh-TW→zh_TW). Regression test added. Thread resolved.
2	CodeRabbit	Skip	No actionable comments.

CI green, all review threads resolved. Ready for review/merge — not self-merging.