fix logic in e2e tests to handle all providers

tests/e2e/features/query.feature

@@ -175,7 +175,7 @@ Scenario: Check if LLM responds for query request with error for missing query
     {"query": "Say hello", "model": "{MODEL}", "provider":"unknown"}
     """
      Then The status code of the response is 404
-      And The body of the response contains Model with ID gpt-4o-mini does not exist
+      And The body of the response contains Model with ID {MODEL} does not exist
 
   @skip-in-library-mode
   Scenario: Check if LLM responds for query request with error for inability to connect to llama-stack

tests/e2e/features/steps/common_http.py

@@ -165,11 +165,17 @@ def check_response_body_schema(context: Context) -> None:
 
 @then("The body of the response contains {substring}")
 def check_response_body_contains(context: Context, substring: str) -> None:
-    """Check that response body contains a substring."""
+    """Check that response body contains a substring.
+
+    Supports {MODEL} and {PROVIDER} placeholders in the substring so
+    assertions work with any configured provider (e.g. unknown-provider
+    error message includes the actual model id).
+    """
     assert context.response is not None, "Request needs to be performed first"
+    expected = replace_placeholders(context, substring)
     assert (
-        substring in context.response.text
-    ), f"The response text '{context.response.text}' doesn't contain '{substring}'"
+        expected in context.response.text
+    ), f"The response text '{context.response.text}' doesn't contain '{expected}'"
 
 
 @then("The body of the response is the following")

tests/e2e/features/streaming_query.feature

@@ -133,7 +133,7 @@ Feature: streaming_query endpoint API tests
     {"query": "Say hello", "model": "{MODEL}", "provider":"unknown"}
     """
     Then The status code of the response is 404
-      And The body of the response contains Model with ID gpt-4o-mini does not exist
+      And The body of the response contains Model with ID {MODEL} does not exist
       And The token metrics should not have changed
 
   Scenario: Check if LLM responds properly when XML and JSON attachments are sent