The plan unit's same-reference gate for a repeated identical /plan selection
(the one uncovered branch in plan-mode/index.ts) gains an explicit case, and
ui-plan's empty node-half apply is exercised the way sibling surface plugins
do (the ui-conversation no-op precedent). Both files read 100% across all
four axes under the CI coverage lane's per-file thresholds.
imccyu
76796df39b