server : support multiple model aliases via comma-separated --alias (#19926)

* server : support multiple model aliases via comma-separated --alias

* server : update --alias description and regenerate docs

* server : multiple model aliases and tags

- address review feedback from ngxson
- --alias accepts comma-separated values (std::set, no duplicates)
- --tags for informational metadata (not used for routing)
- aliases resolve transparently in router via get_meta/has_model
- /v1/models exposes aliases and tags fields

* regenerate docs

* nits

* server : use first alias as model_name for backward compat

address review feedback from ngxson

* server : add single-model test for aliases and tags

tools/server/tests/utils.py

@@ -56,6 +56,7 @@ class ServerProcess:
 
     # custom options
     model_alias: str | None = None
+    model_tags: str | None = None
     model_url: str | None = None
     model_file: str | None = None
     model_draft: str | None = None
@@ -180,6 +181,8 @@ class ServerProcess:
             server_args.extend(["--pooling", self.pooling])
         if self.model_alias:
             server_args.extend(["--alias", self.model_alias])
+        if self.model_tags:
+            server_args.extend(["--tags", self.model_tags])
         if self.n_ctx:
             server_args.extend(["--ctx-size", self.n_ctx])
         if self.n_slots: