fix: update hold-the-line summary to match corrected fixture

public/assets/scenarios/manifest.json

@@ -5,7 +5,7 @@
   },
   "hold-the-line": {
     "name": "Hold the Line",
-    "summary": "10x8 with a forest corridor. Three defenders hold the center against four attackers. Hold the objective for three rounds."
+    "summary": "10x8 with a small forest cluster on the alpha side. Three defenders cover an open objective at (4,4); four bravo units push from the right edge. Hold the objective for three rounds."
   },
   "last-stand": {
     "name": "Last Stand",