Add sniffer playlist removal

[puemos]

Summary

• Add a per-playlist Remove action in the Sniffer list.
• Wire the action through the sniffer controller to the existing playlist removal flow so related levels, inspections, and preferences are cleaned up by existing epics.
• Add a Redux-backed behavior test that removes one sniffed playlist and verifies the rest of the list remains.

Why

Issue #241 asks for a way to delete individual sniffed playlists after using or dismissing them. The store already had removal support, but the Sniffer UI did not expose it.

Validation

• pnpm --filter ./src/popup run test
• pnpm --filter ./src/popup run build