Fix bd-ca0b: bd sync now auto-resolves conflicts instead of failing

Previously, bd sync would fail with "Pre-export validation failed:
refusing to export: JSONL is newer than database" when JSONL was
modified (e.g., after git pull).

Now bd sync intelligently handles this by:
- Detecting when JSONL is newer than the database
- Automatically importing before exporting
- Continuing with the normal sync flow

This makes the workflow much smoother - users can just run 'bd sync'
and it figures out what needs to be done.

Changes:
- Added isJSONLNewer() helper to check file timestamps
- Modified sync command to auto-import when JSONL is newer
- Extracted timestamp check logic for reusability

Resolves: bd-ca0b
🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

cmd/bd/integrity.go

@@ -12,23 +12,34 @@ import (
 	"github.com/steveyegge/beads/internal/types"
 )
 
+// isJSONLNewer checks if JSONL file is newer than database file.
+// Returns true if JSONL is newer, false otherwise.
+func isJSONLNewer(jsonlPath string) bool {
+	jsonlInfo, jsonlStatErr := os.Stat(jsonlPath)
+	if jsonlStatErr != nil {
+		return false
+	}
+
+	beadsDir := filepath.Dir(jsonlPath)
+	dbPath := filepath.Join(beadsDir, "beads.db")
+	dbInfo, dbStatErr := os.Stat(dbPath)
+	if dbStatErr != nil {
+		return false
+	}
+
+	return jsonlInfo.ModTime().After(dbInfo.ModTime())
+}
+
 // validatePreExport performs integrity checks before exporting database to JSONL.
 // Returns error if critical issues found that would cause data loss.
 func validatePreExport(ctx context.Context, store storage.Storage, jsonlPath string) error {
 	// Check if JSONL is newer than database - if so, must import first
-	jsonlInfo, jsonlStatErr := os.Stat(jsonlPath)
-	if jsonlStatErr == nil {
-		beadsDir := filepath.Dir(jsonlPath)
-		dbPath := filepath.Join(beadsDir, "beads.db")
-		dbInfo, dbStatErr := os.Stat(dbPath)
-		if dbStatErr == nil {
-			// If JSONL is newer, refuse export - caller must import first
-			if jsonlInfo.ModTime().After(dbInfo.ModTime()) {
-				return fmt.Errorf("refusing to export: JSONL is newer than database (import first to avoid data loss)")
-			}
-		}
+	if isJSONLNewer(jsonlPath) {
+		return fmt.Errorf("refusing to export: JSONL is newer than database (import first to avoid data loss)")
 	}
 
+	jsonlInfo, jsonlStatErr := os.Stat(jsonlPath)
+
 	// Get database issue count (fast path with COUNT(*) if available)
 	dbCount, err := countDBIssuesFast(ctx, store)
 	if err != nil {