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, 8 insertions, 11 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/indexer/group_index.py b/packages/meshbay-node/src/meshbay_node/indexer/group_index.py
index 2340c78..9e4e780 100644
--- a/packages/meshbay-node/src/meshbay_node/indexer/group_index.py
+++ b/packages/meshbay-node/src/meshbay_node/indexer/group_index.py
@@ -13,29 +13,27 @@ Delta format:
 
 import base64
 import logging
-import os
-import time
-from dataclasses import dataclass, field, asdict
-from pathlib import Path
-from typing import Iterator
+from dataclasses import asdict, dataclass, field
 
 import blake3
 import msgpack
 import zstandard as zstd
 from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
-
 from meshbay_common.crypto import (
+    pk_to_b64,
     sign_chunk,
     verify_chunk_signature,
-    pk_to_b64,
-    generate_gek,
 )
+from meshbay_common.protocol import IndexDelta, IndexEntry
 from meshbay_common.webcrypto import (
     chunk_key_aes as derive_chunk_key,
-    encrypt_chunk_aes as encrypt_chunk,
+)
+from meshbay_common.webcrypto import (
     decrypt_chunk_aes as decrypt_chunk,
 )
-from meshbay_common.protocol import IndexEntry, IndexDelta
+from meshbay_common.webcrypto import (
+    encrypt_chunk_aes as encrypt_chunk,
+)
 
 log = logging.getLogger(__name__)
 
@@ -171,7 +169,6 @@ class GroupIndex:
     ) -> "GroupIndex":
         """Deserialize, verify signature, and decrypt (if private)."""
         from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PublicKey
-        from meshbay_common.crypto import verify_chunk_signature
 
         envelope = msgpack.unpackb(data, raw=False)