Problem: Incremental flush merged dirty issues with existing JSONL, leaving
old IDs when issues were renamed (e.g., test-3 remained after renumbering to test-2).
Solution:
- Add needsFullExport flag to force complete JSONL rebuild from DB
- Skip loading existing JSONL when fullExport=true (start with empty map)
- Use markDirtyAndScheduleFullExport() in renumber and rename-prefix commands
- PersistentPostRun flushes immediately before process exits (respects fullExport)
Test: Verified renumber with gaps correctly exports only current IDs to JSONL
8298cbd375