When a non-launch command (e.g. open, snapshot) triggers auto_launch()
before the explicit launch command is processed, auto_launch() now checks
AGENT_BROWSER_PROVIDER and connects via the provider API instead of
always falling back to a local Chrome instance.
Also redirects daemon stderr to /dev/null when not in debug mode to
prevent crashes from broken pipe after the CLI drops the piped stderr
handle. Cloud providers may write to stderr during connection setup.
Fixes#1125
Related: #979
