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/server.cpp

@@ -92,7 +92,7 @@ int main(int argc, char ** argv) {
 
     // for consistency between server router mode and single-model mode, we set the same model name as alias
     if (params.model_alias.empty() && !params.model.name.empty()) {
-        params.model_alias = params.model.name;
+        params.model_alias.insert(params.model.name);
     }
 
     common_init();