Make lint-backend green, and regenerate the stale client

`wanted_names` never read its `previous` argument — the caller reassigns
`wanted` from the return value — so the parameter goes rather than gaining
an underscore; its one call site and four test calls follow. Sorts the
imports in test_artifacts.py. Both were failing `make lint-backend` at HEAD.

Regenerates the client, which 8cb843e left behind when it corrected the
revoke_client docstring.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CL9zvnnvcp1mvA8o7impxk

backend/fluksio/api/routes/flows.py

@@ -922,9 +922,7 @@ MAX_FRAME_EVENTS = 64
 MAX_MEDIA_NAMES = 32
 
 
-def wanted_names(
-    frame: str, only: set[str] | None, previous: set[str]
-) -> set[str] | None:
+def wanted_names(frame: str, only: set[str] | None) -> set[str] | None:
     """What this client is asking to be sent bytes for, or None if it said
     something else.
 
@@ -1061,7 +1059,7 @@ async def flow_events(websocket: WebSocket, token: str = "") -> None:
                     # say, used to be read as the client going away and cost
                     # it every live update from then on.
                     if receiver.exception() is None:
-                        asked = wanted_names(receiver.result(), only, wanted)
+                        asked = wanted_names(receiver.result(), only)
                         if asked is not None:
                             wanted = asked
                     receiver = asyncio.create_task(websocket.receive_text())