fix: preserve requested sources in quick plans

tests/test_planner_v3.py

@@ -96,6 +96,30 @@ class PlannerV3Tests(unittest.TestCase):
         self.assertEqual(1, len(plan.subqueries))
         self.assertEqual(["reddit", "x"], plan.subqueries[0].sources)
 
+    def test_quick_mode_preserves_explicit_requested_sources(self):
+        raw = {
+            "intent": "product",
+            "freshness_mode": "balanced_recent",
+            "cluster_mode": "debate",
+            "subqueries": [
+                {
+                    "label": "primary",
+                    "search_query": "AI coding agents",
+                    "ranking_query": "What are people saying about AI coding agents?",
+                    "sources": ["reddit", "youtube", "grounding", "digg"],
+                    "weight": 1.0,
+                }
+            ],
+        }
+        plan = planner._sanitize_plan(
+            raw,
+            "AI coding agents",
+            ["reddit", "youtube", "grounding", "digg"],
+            ["reddit", "youtube", "grounding", "digg"],
+            "quick",
+        )
+        self.assertIn("digg", plan.subqueries[0].sources)
+
     def test_default_comparison_uses_all_capable_sources(self):
         plan = planner.plan_query(
             topic="codex vs claude code",