Add for non-time group bys so that it doesn't fail validations (#281)

closes #260

Author: WilliamDee

.changes/unreleased/Bug Fix-20250813-105549.yaml

@@ -0,0 +1,3 @@
+kind: Bug Fix
+body: Fix the prompt to ensure grain is passed even for non-time group by"
+time: 2025-08-13T10:55:49.072094-04:00

src/dbt_mcp/prompts/semantic_layer/query_metrics.md

@@ -81,12 +81,12 @@ Question: "What's our average order value by product category for orders over $1
     - I should first limit results to verify the query works
     Parameters (initial query):
     metrics=["average_order_value"]
-    group_by=[{"name": "product_category", "type": "dimension"}]
+    group_by=[{"name": "product_category", "type": "dimension", "grain":null}]
     where="{{ Dimension('order_value') }} > 100"
     limit=10
     Follow-up Query (after verifying results):
     metrics=["average_order_value"]
-    group_by=[{"name": "product_category", "type": "dimension"}]
+    group_by=[{"name": "product_category", "type": "dimension", "grain":null}]
     where="{{ Dimension('order_value') }} > 100"
     limit=None
 </example>
@@ -131,7 +131,7 @@ Question: "What's our customer satisfaction score by region?"
     If user agrees, then:
     Parameters:
     metrics=["net_promoter_score"]
-    group_by=[{"name": "region", "type": "dimension"}]
+    group_by=[{"name": "region", "type": "dimension", "grain":null}]
     order_by=[{"name": "net_promoter_score", "desc": true}]
     limit=10
 </example>