recon-driven sql composer; pick → compose → execute; llm out of structural sql

api/prompts/pick.user.txt

@@ -0,0 +1,10 @@
+QUESTION:
+{question}
+
+CANDIDATE METRICS (pick one for `metric`):
+{metrics_block}
+
+CANDIDATE COLUMNS (pick from these for `group_by` and `where[*].column`):
+{columns_block}
+
+Return the Pick as JSON (or the error object). No other text.