Cross-domain correspondence repo (renamed to coordination)

This file is a rename artifact. The repo originally introduced as correspondence was renamed to coordination to reflect a broader scope (memos, ADRs, contracts) rather than memo-only correspondence. The active intro memo lives at 2026-04-27-platform-coordination-system.md.

This file should be deleted once the workspace allows it. It is preserved here as a valid (superseded) memo so the indexer continues to pass.