feat: add statement_timeout to SQLAlchemy OTEL spans (#9220)

Queries Postgres for statement_timeout on connection checkout and adds
it as db.statement_timeout attribute on cursor execution spans.

🤖 Generated with [Letta Code](https://letta.com)

Co-authored-by: Letta <noreply@letta.com>

letta/otel/sqlalchemy_instrumentation.py

@@ -120,11 +120,24 @@ def _instrument_engine_events(engine: Engine) -> None:
     if isinstance(engine, AsyncEngine):
         engine = engine.sync_engine
 
+    def checkout(dbapi_conn, connection_record, connection_proxy):
+        """Query and cache statement_timeout on connection checkout."""
+        try:
+            cursor = dbapi_conn.cursor()
+            cursor.execute("SHOW statement_timeout")
+            result = cursor.fetchone()
+            connection_record.info["statement_timeout"] = result[0] if result else None
+            cursor.close()
+        except Exception:
+            connection_record.info["statement_timeout"] = None
+
     def before_cursor_execute(conn, cursor, statement, parameters, context, executemany):
         """Track cursor execution start."""
         if not _config["enabled"]:
             return
 
+        statement_timeout = conn.info.get("statement_timeout")
+
         # Store context for the after event
         context._sync_instrumentation_span = _create_sync_db_span(
             operation_type="cursor_execute",
@@ -132,6 +145,7 @@ def _instrument_engine_events(engine: Engine) -> None:
             additional_attrs={
                 "db.executemany": executemany,
                 "db.connection.info": str(conn.info),
+                "db.statement_timeout": statement_timeout,
             },
         )
 
@@ -163,6 +177,7 @@ def _instrument_engine_events(engine: Engine) -> None:
             context._sync_instrumentation_span = None
 
     # Register engine events
+    event.listen(engine.pool, "checkout", checkout)
     event.listen(engine, "before_cursor_execute", before_cursor_execute)
     event.listen(engine, "after_cursor_execute", after_cursor_execute)
     event.listen(engine, "handle_error", handle_cursor_error)
@@ -170,6 +185,7 @@ def _instrument_engine_events(engine: Engine) -> None:
     # Store listeners for cleanup
     _instrumentation_state["engine_listeners"].extend(
         [
+            (engine.pool, "checkout", checkout),
             (engine, "before_cursor_execute", before_cursor_execute),
             (engine, "after_cursor_execute", after_cursor_execute),
             (engine, "handle_error", handle_cursor_error),