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>

5 files changed, 14 insertions, 12 deletions

diff --git a/packages/meshbay-common/src/meshbay_common/background.py b/packages/meshbay-common/src/meshbay_common/background.py
index 1f25dfd..0afc3e8 100644
--- a/packages/meshbay-common/src/meshbay_common/background.py
+++ b/packages/meshbay-common/src/meshbay_common/background.py
@@ -30,7 +30,8 @@ from __future__ import annotations
 
 import asyncio
 import logging
-from typing import Any, Coroutine
+from collections.abc import Coroutine
+from typing import Any
 
 log = logging.getLogger(__name__)
 
diff --git a/packages/meshbay-common/src/meshbay_common/crypto.py b/packages/meshbay-common/src/meshbay_common/crypto.py
index eadb42b..e537500 100644
--- a/packages/meshbay-common/src/meshbay_common/crypto.py
+++ b/packages/meshbay-common/src/meshbay_common/crypto.py
@@ -5,17 +5,17 @@ Validated in Spike 1 and Spike 6 of the POC.
 All operations use PyCA cryptography (OpenSSL-backed, hardware-accelerated).
 """
 
-import os
 import base64
+import os
 
+import blake3
+from cryptography.hazmat.primitives import hashes, serialization
 from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey, Ed25519PublicKey
 from cryptography.hazmat.primitives.asymmetric.x25519 import X25519PrivateKey, X25519PublicKey
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
 from cryptography.hazmat.primitives.ciphers.aead import ChaCha20Poly1305
-from cryptography.hazmat.primitives.kdf.hkdf import HKDF
 from cryptography.hazmat.primitives.kdf.argon2 import Argon2id
-from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
-from cryptography.hazmat.primitives import hashes, serialization
-import blake3
+from cryptography.hazmat.primitives.kdf.hkdf import HKDF
 
 # ── Key serialisation helpers ─────────────────────────────────────────────────
 
diff --git a/packages/meshbay-common/src/meshbay_common/keyderive.py b/packages/meshbay-common/src/meshbay_common/keyderive.py
index 497f877..4b90af3 100644
--- a/packages/meshbay-common/src/meshbay_common/keyderive.py
+++ b/packages/meshbay-common/src/meshbay_common/keyderive.py
@@ -24,11 +24,11 @@ See keyderive.js for the browser-side implementation.
 """
 
 import hashlib
+
 from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
 from cryptography.hazmat.primitives.asymmetric.x25519 import X25519PrivateKey
 from cryptography.hazmat.primitives.kdf.argon2 import Argon2id
 
-
 # Argon2id parameters — same as keystore (see crypto.py)
 _ITERATIONS  = 3
 _MEMORY_COST = 65536   # 64 MB — increase to 262144 for production
@@ -85,9 +85,11 @@ def encrypt_keypair_bundle(
     Returns: AES-256-GCM ciphertext (nonce prepended).
     """
     import os
+
+    import msgpack
     from cryptography.hazmat.primitives.ciphers.aead import AESGCM
+
     from meshbay_common.crypto import sk_to_raw
-    import msgpack
 
     # Derive an AES key from the password (different info string from key derivation)
     salt = hashlib.sha256(f"meshbay:bundle:v1:{username}".encode()).digest()
diff --git a/packages/meshbay-common/src/meshbay_common/protocol.py b/packages/meshbay-common/src/meshbay_common/protocol.py
index c444711..d6e30e7 100644
--- a/packages/meshbay-common/src/meshbay_common/protocol.py
+++ b/packages/meshbay-common/src/meshbay_common/protocol.py
@@ -32,12 +32,11 @@ which local promise a reply belongs to.
 
 import os
 from dataclasses import dataclass, field
-from typing import Any
 
 # The wire versions live in meshbay_common/__init__.py — one source, because a
 # second copy here said "0.1" while every message on the wire carried "0.2".
 # Nothing imported it, which is the only reason it was harmless.
-from meshbay_common import MNP_VERSION, MHP_VERSION   # noqa: F401  (re-export)
+from meshbay_common import MHP_VERSION, MNP_VERSION  # noqa: F401  (re-export)
 from meshbay_common.groupbox import PURPOSE_UPLOAD, seal, unseal
 from meshbay_common.webcrypto import (
     chunk_key_aes,
@@ -45,7 +44,6 @@ from meshbay_common.webcrypto import (
     encrypt_chunk_aes,
 )
 
-
 # ── MNP message types ─────────────────────────────────────────────────────────
 
 class MNP:
diff --git a/packages/meshbay-common/src/meshbay_common/webcrypto.py b/packages/meshbay-common/src/meshbay_common/webcrypto.py
index 58958f8..3bd5ae6 100644
--- a/packages/meshbay-common/src/meshbay_common/webcrypto.py
+++ b/packages/meshbay-common/src/meshbay_common/webcrypto.py
@@ -26,9 +26,10 @@ This ensures AES and ChaCha20 keys are always distinct even from the same GEK.
 """
 
 import os
+
+from cryptography.hazmat.primitives import hashes
 from cryptography.hazmat.primitives.ciphers.aead import AESGCM
 from cryptography.hazmat.primitives.kdf.hkdf import HKDF
-from cryptography.hazmat.primitives import hashes
 
 
 def chunk_key_aes(gek: bytes, file_hash: bytes, chunk_index: int) -> bytes: