Accept stream query parameter in ingest_segments endpoint
The segments list endpoint derived stream from remote name via
stream_name(remote=...), which calls _strip_hostname and strips
qualifiers like '.tmux' — colliding both observers into one stream.
Now accepts an optional ?stream= query parameter, matching the
pattern already used by ingest_upload. Falls back to deriving
from remote name when not provided.
Prerequisite for standalone solstone-tmux observer extraction.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>