When validateJSONLIntegrity() clears export_hashes due to hash mismatch
or missing JSONL, the subsequent export now correctly exports ALL issues
instead of only dirty ones, preventing permanent database divergence.
Changes:
- validateJSONLIntegrity() returns (needsFullExport, error) to signal when
export_hashes was cleared
- flushToJSONL() moved integrity check BEFORE isDirty gate so integrity
issues trigger export even when nothing is dirty
- Missing JSONL treated as non-fatal force-full-export case
- Increased scanner buffer from 64KB to 2MB to handle large JSON lines
- Added scanner.Err() check to catch buffer overflow errors
- Updated all tests to verify needsFullExport flag
Fixes database divergence issue where clearing export_hashes didn't
trigger re-export, causing 5 issues to disappear from JSONL in fred clone.
Amp-Thread-ID: https://ampcode.com/threads/T-bf2fdcd6-7bbd-4c30-b1db-746b928c93b8
Co-authored-by: Amp <amp@ampcode.com>
## Problem
Export deduplication feature broke when JSONL and export_hashes diverged
(e.g., after git pull/reset). This caused exports to skip issues that
weren't actually in the file, leading to silent data loss.
## Solution
1. JSONL integrity validation before every export
- Store JSONL file hash after export
- Validate hash before export, clear export_hashes if mismatch
- Automatically recovers from git operations changing JSONL
2. Clear export_hashes on all imports
- Prevents stale hashes from causing future export failures
- Import operations invalidate export_hashes state
3. Add Storage interface methods:
- GetJSONLFileHash/SetJSONLFileHash for integrity tracking
- ClearAllExportHashes for recovery
## Tests Added
- TestJSONLIntegrityValidation: Unit tests for validation logic
- TestImportClearsExportHashes: Verifies imports clear hashes
- TestExportIntegrityAfterJSONLTruncation: Simulates git reset (would have caught bd-160)
- TestExportIntegrityAfterJSONLDeletion: Tests recovery from file deletion
- TestMultipleExportsStayConsistent: Tests repeated export integrity
## Follow-up
Created bd-179 epic for remaining integration test gaps (multi-repo sync,
daemon auto-sync, corruption recovery tests).
Closes bd-160
