feat: wire up breadcrumb click navigation

- Click Room → zooms camera to that room
- Click Floor/Building/Facility → returns to isometric overview
- Completes Phase 3 hierarchy navigation spec

frontend/src/pages/Facility3DViewerPage.tsx

@@ -164,6 +164,24 @@ export default function Facility3DViewerPage() {
         setSelectedPlant(null);
     };
 
+    // Breadcrumb navigation handler
+    const handleBreadcrumbNavigate = (level: string) => {
+        if (!floorData || !selectedPlant) return;
+
+        if (level === 'room' && selectedPlant.breadcrumb?.room) {
+            // Find the room by name and focus on it
+            const room = floorData.rooms.find(r => r.name === selectedPlant.breadcrumb?.room);
+            if (room) {
+                focusRoom(room);
+            }
+        } else if (level === 'floor' || level === 'building' || level === 'facility') {
+            // Return to floor overview
+            setCameraPreset('ISOMETRIC');
+            setFocusTarget(null);
+        }
+        // Section/tier clicks stay on current view but could highlight
+    };
+
     // Search result selection handler
     const handleSearchSelect = useCallback((result: any) => {
         if (!floorData) return;
@@ -395,6 +413,7 @@ export default function Facility3DViewerPage() {
                                     section: selectedPlant.breadcrumb.section,
                                     tier: selectedPlant.tier,
                                 }}
+                                onNavigate={handleBreadcrumbNavigate}
                             />
                         </div>
                     )}