add --port flag to sol service install, default 5015
sol service install and make install-service now accept a port for the
convey web server (default 5015). Previously the service used auto-port
which made the URL unpredictable across restarts.
make install-service # port 5015
make install-service PORT=8000 # custom port
sol service install --port 8000 # CLI equivalent
Also removes the stale backlog item for service install (already done)
and documents the service workflow in INSTALL.md, README, and the
coding skill environment reference.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>