Enable tagged Preview 3 custom builds

[ODevStudio]

Summary

• Explicitly allow v3.1.14-preview.3 in the builder, Worker and compatible plugin catalogs.
• Derive custom preview versions from the exact tag, not the default source header: 3.1.14-preview.3-custom.
• Regenerate browser/service catalogs and retain main as default.
• Include the locally reviewed wizard source-version clarification.
• No signing, rollback, retention or free-tier guard changes.

Validation

• 38 Worker/Fleet/configurator/retention tests passed locally.
• Plugin catalog tests passed using current main metadata for the prospective unpublished stable ref only; no stable tag created.
• Preview tag resolves to bcafebe.
• Pressensor patch passes git apply --check on the actual Preview 3 checkout.
• AI documentation contract and git diff --check passed.
• Production tag-based USB baseline and custom-to-custom WiFi hardware tests follow deployment; not yet claimed as passed.