Consolidate the execute_plan CLI handler to eliminate a redundant
service.get_plan() call (the separate read-only pre-check now
reuses the same current_plan reference used for phase detection),
update the command-table description from the stale 'Transition to
Execute phase' to 'Run phase-aware plan execution', and replace
the static post-execution hint with a state-aware message that
distinguishes execute/complete (ready for apply) from other states
(continue executing).
Update corresponding Behave test mocks to match the reduced
get_plan call sequence and the updated output panel title.
ISSUES CLOSED: #967
brent.edwards