fix(cookbook): preserve endpoints across model launches (#6969)

* fix(cookbook): match stale endpoints by launched model, not display name

After registering an LLM endpoint, the Cookbook deleted every other local-*
endpoint with the same display name at a different URL. The display name is
the repo short name, which repos from different orgs share (for example
meta-llama/Llama-3.1-8B-Instruct and unsloth/Llama-3.1-8B-Instruct), so
launching one deleted the endpoint of the other while its server was running.

Match stale endpoints by the full model id they were last launched for,
which is the last entry of their pinned_models. Reusing an endpoint now
moves the launched model to the end of its pins so that entry stays current.

* fix(cookbook): guard endpoint cleanup by serve ownership

Preserve independently launched models instead of sweeping endpoints by display name or mutable model pins.

Bind Cookbook endpoint registrations to their serve sessions and prevent stale watchdogs or scheduled stops from deleting newer registrations.

Reuse the existing endpoint deletion contract to preserve settings, preferences, session cleanup, and cache invalidation.

Cover LLM and image endpoint lifecycle regressions.

---------

Co-authored-by: Alexandre Teixeira <general@alexandreteixeira.dev>

routes/model_routes.py

@@ -3044,20 +3044,44 @@ def setup_model_routes(model_discovery):
         return {"dependents": _settings_using_endpoint(ep_id)}
 
     @router.delete("/model-endpoints/{ep_id}")
-    def delete_model_endpoint(ep_id: str, request: Request):
+    def delete_model_endpoint(
+        ep_id: str,
+        request: Request,
+        expected_cookbook_serve_session_id: Optional[str] = None,
+    ):
         require_admin(request)
         db = SessionLocal()
         try:
             ep = db.query(ModelEndpoint).filter(ModelEndpoint.id == ep_id).first()
             if not ep or not _chatgpt_endpoint_visible(ep, request):
                 raise HTTPException(404, "Endpoint not found")
+            if expected_cookbook_serve_session_id is not None:
+                # The DELETE itself checks ownership. An old serve must never
+                # mutate the settings of an endpoint reused by another serve.
+                if (
+                    not ep_id.startswith(("local-", "img-"))
+                    or not expected_cookbook_serve_session_id
+                ):
+                    raise HTTPException(409, "Cookbook endpoint ownership mismatch")
+                deleted = (
+                    db.query(ModelEndpoint)
+                    .filter(
+                        ModelEndpoint.id == ep_id,
+                        ModelEndpoint.cookbook_serve_session_id
+                        == expected_cookbook_serve_session_id,
+                    )
+                    .delete(synchronize_session=False)
+                )
+                if not deleted:
+                    raise HTTPException(409, "Cookbook endpoint ownership changed")
             # Clean up any settings that reference this endpoint
             cleared = _clear_settings_for_endpoint(ep_id)
             cleared_user_preferences = _clear_user_prefs_for_endpoint(ep_id)
             cleared_sessions = _clear_sessions_for_endpoint(db, ep.base_url, ep.id, ep.owner)
             cleared_loaded_sessions = _clear_loaded_sessions_for_endpoint(ep.base_url, ep.id, ep.owner)
             auth_id = getattr(ep, "provider_auth_id", None)
-            db.delete(ep)
+            if expected_cookbook_serve_session_id is None:
+                db.delete(ep)
             cleared_provider_auth = _delete_orphaned_provider_auth(db, auth_id, exclude_ep_id=ep_id)
             db.commit()
             _invalidate_models_cache()