Validate translation imports and document settings compatibility

[DirkDoes]

Purpose of this PR:

Add an import regression check for YAML structure, duplicate flattened keys/languages, required catalogs, matching placeholders, and category other fallbacks. Missing translations are reported and retain English fallback; existing empty sheet stubs remain unavailable.

Document typed settings, persistence behavior, t()/t_legacy(), category migration, live translation bindings, and merge order. No imported translation files are edited.

Top of the stack, based on #501. Merge bottom-up after the implementation layers.

How to Test:

dotnet test WheelWizard.sln

583 tests passed (563 unit, 20 headless UI). Run dotnet test WheelWizard.sln. The catalog check runs directly against the production embedded resources.

What Has Been Changed:

See the focused implementation above. The existing settings JSON contract and imported translation sheets are preserved.

Related Issue Link:

No linked issue. Part of native GitHub stack #503.

Checklist before merging

• You have created relevant tests

[coderabbitai]

Important

Draft PR not reviewed

Draft PRs are not automatically reviewed by default.

• Trigger a manual review

To automatically review draft PRs, update your CodeRabbit configuration:

reviews:
  auto_review:
    drafts: true

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}