fix(agent-office): critical bug fixes from code review — wall pathfinding, drag/click, DPR, culling

- Pathfinder.setBlocked: remove blocked.clear() to preserve wall tiles set by setWalls()
- Pathfinder.findPath: fix dead-code goal exception — remove redundant isBlocked check, keep goal-tile exception in single guard
- OfficeRenderer: track mouseDownPos/_wasDragging; expose wasDragging() method for click-after-drag suppression
- OfficeRenderer._render: track _lastDpr to detect monitor DPR changes; use setTransform instead of scale to avoid accumulation
- TileMap.render: use clientWidth/clientHeight for viewport culling (CSS space, not buffer pixels)
- TaskTab: wrap JSON.parse in try/catch to prevent crash on malformed result_data

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pages/agent-office/AgentOffice.jsx

@@ -14,7 +14,7 @@ export default function AgentOffice() {
 
   const {
     canvasRef, updateAgentState, setAgentNotification,
-    setTheme, setZoom, hitTest, getZoom
+    setTheme, setZoom, hitTest, getZoom, wasDragging
   } = useOfficeCanvas();
 
   const [selectedAgent, setSelectedAgent] = useState(null);
@@ -37,6 +37,7 @@ export default function AgentOffice() {
 
   // 캔버스 클릭 핸들러
   const handleCanvasClick = useCallback((e) => {
+    if (wasDragging()) return; // 드래그 후 발생하는 클릭 무시
     const result = hitTest(e.clientX, e.clientY);
     if (result.type === 'agent') {
       setSelectedAgent(result.id);
@@ -45,7 +46,7 @@ export default function AgentOffice() {
     } else {
       setSelectedAgent(null);
     }
-  }, [hitTest, clearNotifications, setAgentNotification]);
+  }, [hitTest, clearNotifications, setAgentNotification, wasDragging]);
 
   // 테마 변경
   const handleThemeChange = useCallback((name) => {