fix: preserve stream qualifier in remote ingest (tmux.observer collision)
stream_name(remote="fedora.tmux") calls _strip_hostname which strips
everything after the first dot, treating ".tmux" as a domain suffix.
Both the desktop observer ("fedora") and tmux observer ("fedora.tmux")
were landing in the same "fedora" stream.
Clients already send their canonical stream name in meta["stream"].
Use that value when present instead of re-deriving from the registration
name. Falls back to the old derivation if meta stream is absent/invalid.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>