Data lineage & data maps: future enhancements

[fuseraft]

Consolidated tracking issue for the planned data-lineage capabilities described in docs/features/data-lineage.md and docs/guide/data-maps.md (both "Future Enhancements" sections describe the same underlying data-map subsystem).

• Lineage chaining — auto-link concepts when one integration's destination system matches another's source system, enabling multi-hop lineage queries (docs/features/data-lineage.md#lineage-chaining-future-feature)
• Graph visualization — compendium lineage graph --bundle my-catalog --output lineage.svg, producing a directed graph of data flows across systems
• Impact analysis tool — CLI command to trace all downstream effects of a given source/field
• Column-level lineage — track individual field transformations across multiple hops
• Lineage validation — detect broken connections (a data map's destination system doesn't exist)
• Merge tracking — track when multiple source files contribute to the same integration concept
• CSV export — export data map concepts back to normalized CSV for version control

Split any of these into their own issue once someone picks it up — this is a checklist, not a single PR.