Refactor port allocation: supervisor discovers port, convey requires it
Move dynamic port discovery from convey CLI to supervisor so the port
is known before launching convey. Supervisor now prints the Convey URL
on startup. Convey CLI requires --port (no default), and `sol start`
accepts optional port argument (0 = auto-select).
- supervisor.py: find available port, pass to convey, print URL
- convey/cli.py: require --port, remove port discovery logic
- convey/screenshot.py: make port required parameter
- convey/__init__.py: remove unused run_service export
- docs/INSTALL.md: update to reference dynamic port
- think/mcp.py: clarify cortex uses dynamic port in help text
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>