WS-B.1: data.go mechanical file split (verb-file convention)

[LukasWodka]

Part of epic tracebloc/backend#1106. Full spec: report §5 (mirrored on the epic; artifact https://claude.ai/code/artifact/b4b6e6a6-4d76-4e46-a668-6f4f0f944344). WS-B PR1: mechanical moves within package cli — data_ingest_cmd.go (flag surface + misapplied-flag guards ~350 ln), data_ingest_local.go, data_ingest_cluster.go, data_ingest_output.go (writePushJSON/classifyPushOutcome kept together). data_test.go compiles unchanged. Zero behavior change, diff-stat provably mechanical.

[LukasWodka]

Shipped in #303 (merged to develop). Closing as completed — CLI refactor epic backend#1106 cleanup.