fix: clear all mypy errors

Annotate untyped containers and Optional attributes, type the stdlib-shaped
metric dicts in the client plugins, and add types-PyYAML/types-psutil to the
dev extras plus a mypy override for nio/mattermostdriver (no stubs).

Behaviour fixes found on the way: enable_kernel_timestamps() now returns False
when SO_TIMESTAMP is unknown instead of raising TypeError, send_shutdown is
defined at module level so cleanup() cannot hit a NameError, and a failed
subprocess returncode falls back to UNKNOWN.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

hbd/common/proto.py

@@ -92,7 +92,7 @@ def stodict(msg: bytes):
     '!' and decodes accordingly. Returns a dict with key 'ID' set to the
     message ID and the parsed key/value pairs.
     """
-    d = {}
+    d: Dict[str, Any] = {}
     if len(msg) > 0 and chr(msg[0]) == "!":
         # message is: b'!ID:' + compressed_payload
         # original code used msg[1:4].decode() for ID (3 bytes including colon)