[jacquard-oauth] add new scope types, index structures, and validation infrastructure
- Add TransitionScope::ChatBsky variant with parsing, serialisation, and grants
- Add IncludeScope<S> type and Scope::Include variant with percent-encoded audience
- Add scope index types (ScopeIndices, ScopeInnerIndices, RepoActionFlags, etc.)
- Make validate_did and validate_nsid public in jacquard-common
- Add MimePattern validation and unchecked constructor