Completion status previously lived only in my in-session TodoWrite list
(ephemeral, doesn't survive the session) or had to be inferred from which
steps had an entry in the execution log. Neither is a durable, explicit
answer to "what's left."
Adds a markdown checklist at the top of each plans-executions file, one
line per plan step, checked in the same commit as that step's entry. A
new session resuming this plan can read the file alone and know exactly
where to pick up.
Co-Authored-By: Claude <noreply@anthropic.com>