fix: Fix daemon export leaving JSONL newer than database (issues #301, #321)

After daemon auto-export, JSONL mtime could be newer than database mtime
due to SQLite WAL mode not updating beads.db until checkpoint. This caused
validatePreExport to incorrectly block subsequent exports with "JSONL is
newer than database" error, leading to daemon shutdown.

Solution: Call TouchDatabaseFile after all export operations to ensure
database mtime >= JSONL mtime. This prevents false positives in validation

cmd/bd/export.go

@@ -385,6 +385,18 @@ Output to stdout by default, or use -o flag for file output.`,
 			fmt.Fprintf(os.Stderr, "  Mismatch indicates export failed to write all issues\n")
 			os.Exit(1)
 		}
+
+			// Update database mtime to be >= JSONL mtime (fixes #278, #301, #321)
+			// Only do this when exporting to default JSONL path (not arbitrary outputs)
+			// This prevents validatePreExport from incorrectly blocking on next export
+			if output == "" || output == findJSONLPath() {
+				beadsDir := filepath.Dir(finalPath)
+				dbPath := filepath.Join(beadsDir, "beads.db")
+				if err := TouchDatabaseFile(dbPath, finalPath); err != nil {
+					// Log warning but don't fail export
+					fmt.Fprintf(os.Stderr, "Warning: failed to update database mtime: %v\n", err)
+				}
+			}
 	}
 
 	// Output statistics if JSON format requested