style: ruff's own fixes, mechanically applied

`ruff check .` had gone unrun long enough to report 568 errors, which is the
same as having no linter: the next real finding would have been invisible in the
noise. This is the 521 it fixes by itself, in 173 files, and nothing else — the
98 it cannot fix are the next commit.

What actually changed: import sorting (225), imports nobody used (87, none of
them a re-export — no `__init__.py` is touched, which was the one way this could
have broken an import elsewhere), `datetime.timezone.utc` to `datetime.UTC` (69)
and `asyncio.TimeoutError` to `TimeoutError` (18), both plain aliases on the 3.12
this project requires, `Optional[X]` to `X | None` (24), and f-strings with
nothing to interpolate (19).

Checked rather than assumed: every module in the three packages still imports,
and the suite is 2893 passed — the same count, test for test, as the merge
before it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 2 insertions, 3 deletions

diff --git a/packages/meshbay-common/tests/test_handshake.py b/packages/meshbay-common/tests/test_handshake.py
index d4f6d2b..11313aa 100644
--- a/packages/meshbay-common/tests/test_handshake.py
+++ b/packages/meshbay-common/tests/test_handshake.py
@@ -12,7 +12,6 @@ import jwt
 import pytest
 from cryptography.hazmat.primitives import serialization
 from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
-
 from meshbay_common.handshake import (
     HANDSHAKE_PREFIX,
     NONCE_LEN,
@@ -207,8 +206,8 @@ def test_membership_refusal_carries_a_code_a_client_can_act_on():
     is exactly the kind of coupling that breaks when someone improves a message.
     """
     import jwt as _jwt
-    from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
     from cryptography.hazmat.primitives import serialization
+    from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
 
     sk = Ed25519PrivateKey.generate()
     pem_priv = sk.private_bytes(
@@ -234,8 +233,8 @@ def test_a_group_this_node_does_not_host_is_refused_with_a_code():
     dark on 2026-09-11 with its real host online — or had to match on wording.
     """
     import jwt as _jwt
-    from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
     from cryptography.hazmat.primitives import serialization
+    from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
 
     sk = Ed25519PrivateKey.generate()
     pem_priv = sk.private_bytes(