[READ-ONLY] Mirror of https://github.com/okikio/opfs.

docs(architecture): explain driver and provider boundaries master

Previous documentation described the storage stack less clearly than the current refactor uses it in code. Document the driver -> adapter -> FileSystemType -> bridge model, update the API and design guides around limit provenance and planning, and refresh the provider docs so reviewers and users can understand the intent of the new architecture before reading implementation details.