After the fullscreen Plan Review closed on approve-and-execute, the
conversation view stayed blank while the plan ran. The propose write's
tool_execution_end handler runs inside EventController's serialized
dispatch chain and awaited handlePlanApproval, which awaits session.prompt
for the entire execution turn, so every later agent_start/message_start/
tool/message_update event queued behind it until the run finished.
Detach the approval dispatch so the dispatch link settles immediately and
the execution turn's events render live. Follow-up to #5688, which only
moved the overlay close before the still-blocking dispatch.
Fixes#7684
roboomp