Preserve social history across profile renames

[pRizz]

Summary

• accept current X oEmbed provider and wording while retaining strict provider and placeholder validation
• isolate public-cache entries by link ID and resolved source URL, and preserve same-source last-known-good metadata on regressions
• add a guarded social profile rename CLI, repo skill, validation, docs, and history-continuity regression coverage

Validation

• bun run biome:check
• bun run studio:lint
• bun run typecheck
• bun run studio:typecheck
• bun run --filter @openlinks/studio-api test
• bun run studio:test:integration
• focused enrichment, cache, CLI, validator, and follower-history tests
• bun run enrich:rich:strict
• bun run validate:data
• bun run build
• bun run quality:check
• bun run ci:required
• Studio API, web, and worker Docker builds
• rename skill validator and clean forward dry-run

The branch was rebuilt directly from upstream/main. All paths declared by config/fork-owned-paths.json are excluded from the diff.

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