LCORE-1422: Replace @InlineRAG magic tag with explicit Background step

Replace the implicit @InlineRAG feature tag (handled in environment.py
hooks) with a parameterized Background step "The service uses the
{config_name} configuration" that switches config and restarts the
container. The step is reusable for any config file and idempotent
within a feature run via backup file existence check.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: are-ces

tests/e2e/features/inline_rag.feature

@@ -1,9 +1,9 @@
-@InlineRAG
 Feature: Inline RAG (BYOK) support tests
 
   Background:
     Given The service is started locally
       And REST API service prefix is /v1
+      And The service uses the lightspeed-stack-inline-rag.yaml configuration
 
   Scenario: Check if inline RAG source is registered
     Given The system is in default state

tests/e2e/features/steps/common.py

@@ -5,6 +5,14 @@
 from behave import given  # pyright: ignore[reportAttributeAccessIssue]
 from behave.runner import Context
 
+from tests.e2e.utils.utils import (
+    create_config_backup,
+    is_prow_environment,
+    restart_container,
+    switch_config,
+    wait_for_container_health,
+)
+
 
 @given("The service is started locally")
 def service_is_started_locally(context: Context) -> None:
@@ -23,6 +31,34 @@ def service_is_started_locally(context: Context) -> None:
     context.port_llama = os.getenv("E2E_LLAMA_PORT", "8321")
 
 
+@given("The service uses the {config_name} configuration")  # type: ignore
+def configure_service(context: Context, config_name: str) -> None:
+    """Switch to the given configuration if not already active.
+
+    On first call creates a backup of the current config, switches to the
+    named config, and restarts the container.  Subsequent calls within
+    the same feature are no-ops (detected by backup file existence in Docker
+    or backup key presence in Prow).
+
+    Parameters:
+        context (Context): Behave context.
+        config_name (str): Config filename (e.g. lightspeed-stack-inline-rag.yaml).
+    """
+    if not is_prow_environment() and os.path.exists("lightspeed-stack.yaml.backup"):
+        return
+
+    mode_dir = "library-mode" if context.is_library_mode else "server-mode"
+    if is_prow_environment():
+        config_path = f"tests/e2e-prow/rhoai/configs/{config_name}"
+    else:
+        config_path = f"tests/e2e/configuration/{mode_dir}/{config_name}"
+    create_config_backup("lightspeed-stack.yaml")
+    switch_config(config_path)
+    restart_container("lightspeed-stack")
+    # Library mode needs extra time to load embedding models after restart
+    wait_for_container_health("lightspeed-stack", max_attempts=12)
+
+
 @given("The system is in default state")
 def system_in_default_state(context: Context) -> None:
     """Check the default system state.