Java conversion: CICS FILE (VSAM) operations + FILE-CONTROL / IDCAMS -> Spring Data repositories

[squid-protocol]

READ / WRITE / REWRITE / DELETE / browse on a FILE become repository methods on an entity keyed by the cluster's RECORD KEY (offset / length checked against IDCAMS KEYS).

Part of the COBOL→Java conversion epic.

🤖 Generated with Claude Code