New plans table (id, project_id, title, description, status, flow_run_id,
progress_pct, items_total, items_completed, metadata, timestamps) with
CHECK constraints and indexes.
Plan store (plan-store.ts): createPlan, getPlan, listPlans, listActivePlans,
updatePlan, updatePlanFromRun, findPlanWithRunningRun, planStatusFromRun.
Flow-runner integration: onRunTerminal callback fires on every terminal
transition (complete/fail/cancel) and updates linked plans automatically.
5 API endpoints: GET /api/plans, GET /api/plans/active, GET /api/plans/:id,
POST /api/plans, PATCH /api/plans/:id.
484 tests pass, build clean.
