chore: auto-commit (5 archivos)

- playground/tables/CMakeLists.txt
- playground/tables/data_table.cpp
- playground/tables/self_test.cpp
- playground/tables/tql_duckdb.cpp
- playground/tables/tql_duckdb.h

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

playground/tables/tql_duckdb.h

@@ -0,0 +1,29 @@
+// tql_duckdb: ejecuta SQL DuckDB sobre TableInputs in-memory.
+// Solo se compila si FN_TQL_DUCKDB esta definido. Adapter opcional para
+// tql_to_sql emit -> execute. Ver issue 0080.
+#pragma once
+
+#ifdef FN_TQL_DUCKDB
+
+#include "data_table_logic.h"
+#include <string>
+#include <vector>
+
+namespace tql_duckdb {
+
+struct Result {
+    data_table::StageOutput out;
+    std::string error;            // non-empty si fallo
+    int         row_count = 0;
+    double      duration_ms = 0.0;
+};
+
+// Impure: abre DuckDB in-memory, registra tablas como CREATE TABLE + INSERT,
+// prepara sql con `?` placeholders bound a `params`, materializa resultado.
+Result execute(const std::string& sql,
+                const std::vector<std::string>& params,
+                const std::vector<data_table::TableInput>& tables);
+
+} // namespace tql_duckdb
+
+#endif // FN_TQL_DUCKDB