chore: ruff auto-fixes — collapsible-else-if, if-stmt-min-max, dict.fromkeys (#23926)

PLR5501 (collapsible-else-if): 28 instances — else: if: → elif:
PLR1730 (if-stmt-min-max):   15 instances — if x<y: x=y → x=max(x,y)
C420   (dict.fromkeys):       2 instances — dictcomp → dict.fromkeys
PLR1704 (redefined-argument): 1 instance — reason → err_msg (shadow fix)
C414   (unnecessary-list):    1 instance — sorted(list(x)) → sorted(x)

28 files, -44 net lines. All mechanical, zero logic changes.
17,211 tests pass, zero regressions.

gateway/platforms/helpers.py

@@ -246,7 +246,7 @@ class ThreadParticipationTracker:
         thread_list = list(self._threads)
         if len(thread_list) > self._max_tracked:
             thread_list = thread_list[-self._max_tracked:]
-            self._threads = {thread_id: None for thread_id in thread_list}
+            self._threads = dict.fromkeys(thread_list)
         atomic_json_write(path, thread_list, indent=None)
 
     def mark(self, thread_id: str) -> None:

gateway/platforms/qqbot/chunked_upload.py

@@ -592,8 +592,7 @@ async def _run_with_concurrency(
     concurrency: int,
 ) -> None:
     """Run a list of thunks with a bounded number in flight at once."""
-    if concurrency < 1:
-        concurrency = 1
+    concurrency = max(concurrency, 1)
     sem = asyncio.Semaphore(concurrency)
 
     async def _wrap(thunk: Callable[[], Awaitable[None]]) -> None: