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, 6 deletions

diff --git a/poc/spike3_node.py b/poc/spike3_node.py
index c0ddde0..0b6d694 100644
--- a/poc/spike3_node.py
+++ b/poc/spike3_node.py
@@ -12,12 +12,17 @@ Sequence:
   8. Simulate token refresh
 """
 
-import asyncio, httpx, base64, json, os, time
+import asyncio
+import base64
+import json
+import time
 from pathlib import Path
+
+import httpx
+import jwt
+from cryptography.hazmat.primitives import serialization
 from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
 from cryptography.hazmat.primitives.asymmetric.x25519 import X25519PrivateKey
-from cryptography.hazmat.primitives import serialization
-import jwt
 
 HUB_URL    = "http://meshbay.org"
 STATE_FILE = Path("node_state.json")   # persists keys and tokens between runs
@@ -52,7 +57,7 @@ def _load_or_generate_keys(state: dict) -> tuple:
         sk_x  = X25519PrivateKey.generate()
         state["sk_ed25519_b64"] = _sk_to_b64(sk_ed)
         state["sk_x25519_b64"]  = _sk_to_b64(sk_x)
-        print(f"  Generated new keypair")
+        print("  Generated new keypair")
     return sk_ed, sk_x
 
 # ── Main ──────────────────────────────────────────────────────────────────────
@@ -101,7 +106,7 @@ async def main():
             state["user_id"] = r.json()["user_id"]
             print(f"  {PASS} Registered — user_id={state['user_id'][:8]}...")
         elif r.status_code == 409:
-            print(f"  Already registered (409) — continuing with existing account")
+            print("  Already registered (409) — continuing with existing account")
         else:
             raise RuntimeError(f"Register failed: {r.status_code} {r.text}")
 
@@ -149,7 +154,7 @@ async def main():
         node_id = r.json()["node_id"]
         state["node_id"] = node_id
         print(f"  {PASS} Node announced — node_id={node_id[:8]}...")
-        print(f"  endpoint_hint : None (STUN/UPnP discovery in Spike 4)")
+        print("  endpoint_hint : None (STUN/UPnP discovery in Spike 4)")
 
         # ── Step 7: Retrieve node record ──────────────────────────────────────
         print("\n[ 7 ] Retrieve node record from hub")