Prepare v0.3.1 Registry Guidance Cleanup release

[Wonderforge-Lab]

Summary

Release-prep only for v0.3.1 - Registry Guidance Cleanup.

Changes exactly three release-facing files:

• README.md
• locales/zh-CN/README.md
• archive/20260903_v0.3.1_registry_guidance_cleanup.md

This PR:

• updates the English front door to identify v0.3.1 as the latest published scaffold release;
• mirrors that release status and scope in Simplified Chinese;
• adds one repository-resident bilingual revision note with matching English and Simplified-Chinese release notes;
• records the corrective PR validation and patch-level compatibility boundary.

No runtime protocol, schemas, machine fields, statuses, generated views, permissions, or routing rules are changed by this PR.

The GitHub release/tag should be created only after this PR is merged, and should point to the exact resulting main commit.