Adds a priority-ordered, checkbox-format roadmap that the
orchestrator maintains. Three states (`[ ]` open / `[~]` in
progress / `[x]` done), four kinds (milestone / feature / todo /
idea), four priorities (P0..P3). Initial population lifts the
queued items from the JOURNAL tail.
JOURNAL's role narrows: chronological decisions log only, no
forward queue. CLAUDE.md "Roles of ..." section updated to
reflect the split.
