Save button downloads a non-empty PDF

Walk the CVL editor end-to-end: agent + human cooperation, bullet reorder across panes, edit latency, micro-interaction polish, full-list reorder, the header drag chip layout, and the export path. Catches Svelte hydration regressions and CRDT merge ordering bugs the unit tests cannot.

CVL editor and Node-tree micro-contract proof. The intentionally excluded flaky micro specs remain outside this dispatch lane until their handler timing is repaired.