tests: standardize on embedded tests (migrate all from tests/ to lisp/ sources)

lisp/system-model-provider.lisp

@@ -116,3 +116,20 @@ If API-KEY is nil, reads from environment."
 (defskill :passepartout-system-model-provider
   :priority 50
   :trigger (lambda (ctx) (declare (ignore ctx)) nil))
+
+(eval-when (:compile-toplevel :load-toplevel :execute)
+  (ql:quickload :fiveam :silent t))
+
+(defpackage :passepartout-llm-gateway-tests
+  (:use :cl :passepartout)
+  (:export #:llm-gateway-suite))
+
+(in-package :passepartout-llm-gateway-tests)
+
+(fiveam:def-suite llm-gateway-suite :description "Tests for the LLM provider backend")
+(fiveam:in-suite llm-gateway-suite)
+
+(fiveam:test test-provider-rejects-bad-keyword
+  "Verify that provider-openai-request returns :error for an unregistered provider."
+  (let ((result (provider-openai-request "hello" "test" :provider :not-a-real-provider)))
+    (fiveam:is (eq (getf result :status) :error))))