Summary

When a binary channel name that is not valid UTF-8 is subscribed via positional arguments (without a callback handler), the PubSub.on_connect reconnection logic raises UnicodeDecodeError. This happens because on_connect force-decodes every stored channel key to pass it as a keyword argument to subscribe()/psubscribe().

The fix splits channels into two groups during reconnection:

• With handlers (originally passed as kwargs): decoded and re-passed as kwargs — their names are guaranteed decodable since Python requires string keyword arguments
• Without handlers (originally passed as positional args): passed as raw positional args — no decoding required, preserving arbitrary binary names

Changes

• redis/client.py — sync PubSub.on_connect: split channels, patterns, and shard_channels by handler presence
• redis/asyncio/client.py — async PubSub.on_connect: same split for channels and patterns
• tests/test_pubsub.py — added test_resubscribe_binary_channel_on_reconnection and test_resubscribe_binary_pattern_on_reconnection
• tests/test_asyncio/test_pubsub.py — async equivalents of the above tests

Test plan

• New tests subscribe to deliberately invalid UTF-8 channel/pattern names, force a disconnect, then verify get_message() triggers reconnection and resubscription without raising UnicodeDecodeError
• Existing reconnection tests (test_resubscribe_to_channels_on_reconnection, test_resubscribe_to_patterns_on_reconnection) continue to pass, confirming backward compatibility for string channel names with and without handlers

Fixes #3912