chore(release): 0.0.3

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

mail_intake/credentials/store.py

@@ -19,9 +19,8 @@ or secrets managers—without coupling authentication logic to any
 specific storage mechanism.
 """
 
-
 from abc import ABC, abstractmethod
-from typing import Generic, Optional, TypeVar
+from typing import Generic, TypeVar
 
 T = TypeVar("T")
 
@@ -48,12 +47,12 @@ class CredentialStore(ABC, Generic[T]):
     """
 
     @abstractmethod
-    def load(self) -> Optional[T]:
+    def load(self) -> T | None:
         """
         Load previously persisted credentials.
 
         Returns:
-            Optional[T]:
+            T | None:
                 An instance of type `T` if credentials are available and
                 loadable; otherwise `None`.