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_node.py b/poc/spike5_node.py
index 6104e00..b560dc1 100644
--- a/poc/spike5_node.py
+++ b/poc/spike5_node.py
@@ -14,13 +14,19 @@ Note: node initiates the TCP connection (reversed for POC — in production,
 the QUIC client connects to the node using the hole-punching from Spike 4).
 """
 
-import asyncio, json, base64, struct, os, time
+import asyncio
+import base64
+import json
+import os
+import struct
+import time
 from pathlib import Path
+
+import blake3
+from cryptography.hazmat.primitives import hashes, serialization
 from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
 from cryptography.hazmat.primitives.ciphers.aead import ChaCha20Poly1305
 from cryptography.hazmat.primitives.kdf.hkdf import HKDF
-from cryptography.hazmat.primitives import hashes, serialization
-import blake3
 
 MESHBAY_HOST = "meshbay.org"
 MESHBAY_PORT = 19003
@@ -125,7 +131,7 @@ async def main():
     print(f"  {PASS} Test file: {TEST_FILE} ({file_size/1024/1024:.1f} MB)")
 
     # Pre-compute file hash (used in HKDF info string — identifies the file)
-    print(f"  Computing file hash...")
+    print("  Computing file hash...")
     t0 = time.perf_counter()
     file_hash = blake3.blake3(TEST_FILE.read_bytes()).digest()
     print(f"  {PASS} File hash: {file_hash.hex()[:16]}... ({(time.perf_counter()-t0)*1000:.0f}ms)")
@@ -166,7 +172,7 @@ async def main():
 
     print(f"  {PASS} Sent {payload_kb:.1f} KB in {send_ms:.0f}ms ({throughput:.1f} MB/s)")
     print(f"\n  {'='*50}")
-    print(f"  Timings (node side):")
+    print("  Timings (node side):")
     print(f"    Encrypt + sign : {enc_ms:.1f} ms")
     print(f"    TCP send       : {send_ms:.0f} ms")
     print(f"    Total          : {total_ms:.0f} ms")