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, 11 insertions, 5 deletions

diff --git a/poc/spike5_client.py b/poc/spike5_client.py
index 11b3ac0..6ac2fba 100644
--- a/poc/spike5_client.py
+++ b/poc/spike5_client.py
@@ -12,12 +12,18 @@ Acts as the "file requester":
   - Reports timing and results
 """
 
-import asyncio, json, base64, struct, time, sys
+import asyncio
+import base64
+import json
+import struct
+import sys
+import time
+
+import blake3
+from cryptography.hazmat.primitives import hashes
 from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PublicKey
 from cryptography.hazmat.primitives.ciphers.aead import ChaCha20Poly1305
 from cryptography.hazmat.primitives.kdf.hkdf import HKDF
-from cryptography.hazmat.primitives import hashes
-import blake3
 
 PORT        = 19003
 CHUNK_INDEX = 0
@@ -115,7 +121,7 @@ async def handle_node(reader, writer):
     total_ms  = recv_ms + verify_ms
 
     print(f"\n  {'='*50}")
-    print(f"  Timings:")
+    print("  Timings:")
     print(f"    Network receive : {recv_ms:.0f} ms")
     print(f"    Verify+decrypt  : {verify_ms:.1f} ms")
     print(f"    Total           : {total_ms:.0f} ms")
@@ -133,7 +139,7 @@ async def main():
     async with server:
         try:
             await asyncio.wait_for(server.serve_forever(), timeout=30)
-        except asyncio.TimeoutError:
+        except TimeoutError:
             print(f"  {FAIL} Timeout — node did not connect within 30s")
             sys.exit(1)