Add the motivating map-chain integration test: draft -> check, where check
re-routes to draft via script `_next` until an item-local attempts counter
reaches 2, run with validate_before_run on. A sibling test drives the same
map node against a parent state to pin that only collect_into lands on the
parent and that no chain visit touches the parent's loop counts.
Extend bundled_graph_agents_parse_and_validate: the sorted (node, warning)
set of every bundled graph must equal the set the pre-subgraph validator
produced, and graph.example.yaml must load through GraphParser, validate
without errors, and declare a writer for its map's output_key.
Dark-Alex-17
c10965cd71