feat(i18n): complete native translations for every Docsy locale

[Vonng]

Closes #38.

What changed

• Completes native OINK UI text for every locale filename shipped by google/docsy@64f51c5bde2abd2e8a001cb31b32656f5800ca56: 31 Docsy-compatible catalogs plus OINK's generic zh alias, 32 catalogs total.
• Keeps the English authority at 192 keys and removes generated English fallback blocks from the 28 previously incomplete non-English catalogs.
• Preserves runtime placeholders exactly, keeps generic zh identical to zh-cn, and keeps Serbian Latin exactly transliterated from Serbian Cyrillic.
• Removes the fallback-producing bin/check-i18n.py --sync path.
• Makes the owning checker enforce the exact locale set, supported scalar forms and inline comments, key and placeholder parity, hidden-bidi exclusion, distinct callout labels, reviewed English-identical terms, Simplified Chinese alias parity, Serbian script parity, and an all-locale Hugo render that compares every placeholder-free rendered value.
• Documents the Hugo 0.160.x requirement for non-default generic zh beside the regional Chinese catalogs: use locale: zh-CN; bare zh works in this configuration from Hugo 0.161.

Adversarial review

Claude Code Fable 5 at xhigh effort reviewed the implementation in three passes. The first pass found a real Hugo 0.160.1 incompatibility, translation errors, and checker gaps. After those fixes, an independent review found two more checker holes involving YAML inline comments and HTML entity encoding; both were reproduced, fixed, mutation-tested, and included in the final Fable pass. Final verdict: PASS, with no P0/P1/P2 finding remaining.

Verification

• python3 bin/check-i18n.py: 32 locales × 192 keys.
• The same checker passes with Hugo Extended 0.160.1, 0.161.0, and 0.165.0.
• Adversarial probes reject missing, extra, duplicate and nested keys; fallback markers; braced, printf, and Go-template placeholder drift; unreviewed English copies including all three inline-comment styles; hidden bidi controls; callout collisions; and Serbian transliteration drift.
• Legal apostrophes, quoted #, ampersands, and HTML entity round trips pass the runtime comparison.
• hugo --source tests/site --printPathWarnings --printI18nWarnings --panicOnWarning.
• Sibling documentation site with a local module replacement:
  • full npm test;
  • Playwright: 29 WCAG + 45 responsive/palette + 16 keyboard + 10 content + 18 code-block + 4 PRD5 + 5 theme-colour = 127 tests.

Integration and release state

The maintainer explicitly promoted this exact green head to main on 2026-09-03. Source integration is not a published module release: if #37 proceeds, its v1.0.1 tag must remain bound to the already frozen 9a0c0bd patch candidate. These locale catalogs belong to a later minor release.