fix: replace stale entry in a2a.types.__all__ with actual import name (#902)

- Fix stale `__all__` entry in `src/a2a/types/__init__.py`:
`AuthenticatedExtendedCardNotConfiguredError` does not exist in the
module namespace - the actual import is
`ExtendedAgentCardNotConfiguredError`. This caused `AttributeError` at
runtime on `from a2a.types import *` or any direct reference to the
listed name.
- Enable ruff's
[F822](https://docs.astral.sh/ruff/rules/undefined-export/) rule for
`__init__.py` files by adding `preview = true` and
`explicit-preview-rules = true` under `[tool.ruff.lint]`. This prevents
stale `__all__` entries from going undetected in the future, without
introducing any new preview-only rules.

Author: ishymko

pyproject.toml

@@ -199,6 +199,8 @@ indent-width = 4 # Google Style Guide §3.4: 4 spaces
 target-version = "py310" # Minimum Python version
 
 [tool.ruff.lint]
+preview = true
+explicit-preview-rules = true
 ignore = [
     "COM812", # Trailing comma missing.
     "FBT001", # Boolean positional arg in function definition

src/a2a/types/__init__.py

@@ -93,14 +93,14 @@
     'AgentProvider',
     'AgentSkill',
     'Artifact',
-    'AuthenticatedExtendedCardNotConfiguredError',
     'AuthenticationInfo',
     'AuthorizationCodeOAuthFlow',
     'CancelTaskRequest',
     'ClientCredentialsOAuthFlow',
     'ContentTypeNotSupportedError',
     'DeleteTaskPushNotificationConfigRequest',
     'DeviceCodeOAuthFlow',
+    'ExtendedAgentCardNotConfiguredError',
     'ExtensionSupportRequiredError',
     'GetExtendedAgentCardRequest',
     'GetTaskPushNotificationConfigRequest',