feat(pathfinding): add A* vs Dijkstra compare mode

Show A* and Dijkstra side by side on the same grid with visited count and path length. Also clamp typed grid sizes above the max instead of crashing.

src/assets/i18n/en.json

@@ -430,6 +430,8 @@
     "CLEAR_BOARD": "Empty Board",
     "VISITED": "Visited",
     "PATH": "Path",
+    "COMPARE": "Compare (A* vs Dijkstra)",
+    "VISITED_NODES": "Visited nodes",
     "PATH_LENGTH": "Path length",
     "EXECUTION_TIME": "Execution Time",
     "EXPLANATION": {