Feature Request

Is your feature request related to a problem? Please describe.

• ckb export only supports exporting from genesis up to a target block height.
• ckb import fully validates all data using Switch::NONE, which is slow.
• Exported data is in JSON format, making it hard to merge splits like a.json (1–1,000,000) and b.json (1,000,001–1,000,100).

Describe the solution you'd like

1. Support arbitrary height ranges in ckb export (e.g., --from <start> … --to <end>).
2. Add optional flags to ckb import to skip certain checks, speeding up large imports.
3. Support JSONL output format ? in export for easy merging and processing of segmented data files.