Squash-merge lib-standardisation: adopt repo standards across packaging,
tooling, docs, and CI.
- standardize pyproject.toml (canonical packaging, lint config, extras, GSDFC pydoclint)
- add py.typed marker, modernize type hints and Google-style docstrings
- nest generated docs under docs/lib and docs/mcp; add hand-written wiki
- adopt standard Type A PyPI CI pipeline (tag==version guard + quality gate)
- promote generated CHANGELOG.md; bump version to 0.0.3
- Make MailIntakeAuthProvider generic over credential type to enforce
typed auth contracts between providers and adapters
- Refactor Google OAuth provider to use CredentialStore abstraction
instead of filesystem-based pickle persistence
- Remove node-local state assumptions from Google auth implementation
- Clarify documentation to distinguish credential lifecycle from
credential persistence responsibilities
This change enables distributed-safe authentication providers and
allows multiple credential persistence strategies without modifying
auth logic.
