send the map selection to change detection and show the modified class

The comparison hook runs before the selection state is declared in App, so the
selection is read through a getter at the moment the run starts rather than
captured at render. The panel gains the modified count, which until now was
folded into removed plus added.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/types.ts

@@ -1055,7 +1055,13 @@ export interface ChangeDetectionRequest {
   source_dataset_id: string
   target_dataset_id: string
   iou_threshold: number
+  /** Below this the footprints are separate objects rather than one redrawn. */
+  modified_threshold?: number
   include_unchanged: boolean
+  /** Without a selection the comparison covers both datasets in full. */
+  bbox?: VectorSelectionBBox | null
+  area_id?: string | null
+  preview_limit?: number
 }
 
 export interface ChangeDetectionSummary {
@@ -1065,8 +1071,15 @@ export interface ChangeDetectionSummary {
   target_feature_count: number
   added_count: number
   removed_count: number
+  /** A footprint that was redrawn, not demolished and rebuilt. */
+  modified_count?: number
   unchanged_count: number
   iou_threshold: number
+  modified_iou_threshold?: number | null
+  selection_area_id?: string | null
+  /** Counts cover the whole selection; the GeoJSON is capped. */
+  preview_limit?: number | null
+  preview_truncated?: boolean
   warnings: string[]
   generated_at: string
   geojson: GeoJSON.FeatureCollection