Add ThimbleDB Studio and bounded metadata

[Jason-Doyle]

Summary

• add the optional ThimbleDB Studio management frontend to the npm package
• expose matching Node and Cloudflare Studio APIs with explicit scope grants and bounded maintenance operations
• add authenticated snapshot and trie size metadata plus a quiescent migration command for existing collections
• harden browser logout, dormant-cache cleanup, scope switching, and authorization failure handling
• update the generated app, public documentation, website, containers, and package verification

Compatibility

This is a major release because bounded reads fail closed for legacy collections that do not contain authenticated size metadata. Existing point reads remain compatible. Run npx thimbledb migrate-metadata for existing collections while writes are blocked before enabling bounded Studio scans, exports, or retained-deletion views.

Validation

• TypeScript checks
• 185 unit tests
• Chromium, Firefox, and WebKit application and Studio tests
• package and generated-scaffold verification
• Node and Cloudflare starter validation against the packed 3.0.0 artifact
• public site build, tests, and Cloudflare deployment dry run
• local example and comparison harness checks
• dependency audits and GitHub Actions workflow lint
• generic and AWS container builds
• 13 Mermaid diagrams rendered