When importing JSONL that matches the database exactly, import was
reporting '0 created, 0 updated' which was confusing. Now it properly
tracks and reports unchanged issues.
Changes:
- Added Unchanged field to ImportResult
- Track unchanged issues separately from skipped/updated
- Display unchanged count in import summary
- Updated dry-run output to show unchanged count
- Added test to verify correct reporting behavior
Example output: 'Import complete: 0 created, 0 updated, 88 unchanged'
Amp-Thread-ID: https://ampcode.com/threads/T-5dd4843e-9ce3-4fe0-9658-d2227b0a2e4e
Co-authored-by: Amp <amp@ampcode.com>
