#16: handle_screenshot now returns a canonicalized ABSOLUTE path, so the
`✓ Screenshot saved to …` line is the same regardless of process cwd and the
agent can read the file without guessing the cwd.
#15: `session list` now reflects the extension-relay connection — when the relay
is up it shows the active session as `(relay/extension → live Chrome)` instead
of "No active sessions", and the --json output gains a `relay` bool. Stops agents
misjudging a live relay connection as down.