When PROJECT.md exists but planning files are incomplete, onboarding
previously listed /gsd:new-project as a remediation option. That command
errors when the project is already initialized, leaving users at a dead
end. Route partial planning to /gsd:new-milestone instead.
init new-project now uses the same seven-file codebase map completeness
check as init onboard, so partial .planning/codebase/ directories no longer
skip the brownfield mapping offer after onboarding warns about an incomplete
map.
The onboard workflow now branches on onboarding_summary_exists and asks for
confirmation before regenerating SUMMARY.md on repeat runs.
