server: add router multi-model tests (#17704) (#17722)

* llama-server: add router multi-model tests (#17704)

Add 4 test cases for model router:
- test_router_unload_model: explicit model unloading
- test_router_models_max_evicts_lru: LRU eviction with --models-max
- test_router_no_models_autoload: --no-models-autoload flag behavior
- test_router_api_key_required: API key authentication

Tests use async model loading with polling and graceful skip when
insufficient models available for eviction testing.

utils.py changes:
- Add models_max, models_dir, no_models_autoload attributes to ServerProcess
- Handle JSONDecodeError for non-JSON error responses (fallback to text)

* llama-server: update test models to new HF repos

* add offline

* llama-server: fix router LRU eviction test and add preloading

Fix eviction test: load 2 models first, verify state, then load
3rd to trigger eviction. Previous logic loaded all 3 at once,
causing first model to be evicted before verification could occur.

Add module fixture to preload models via ServerPreset.load_all()
and mark test presets as offline to use cached models

* llama-server: fix split model download on Windows

---------

Co-authored-by: Xuan-Son Nguyen <thichthat@gmail.com>

tools/server/tests/utils.py

@@ -7,6 +7,7 @@ import subprocess
 import os
 import re
 import json
+from json import JSONDecodeError
 import sys
 import requests
 import time
@@ -83,6 +84,9 @@ class ServerProcess:
     pooling: str | None = None
     draft: int | None = None
     api_key: str | None = None
+    models_dir: str | None = None
+    models_max: int | None = None
+    no_models_autoload: bool | None = None
     lora_files: List[str] | None = None
     enable_ctx_shift: int | None = False
     draft_min: int | None = None
@@ -143,6 +147,10 @@ class ServerProcess:
             server_args.extend(["--hf-repo", self.model_hf_repo])
         if self.model_hf_file:
             server_args.extend(["--hf-file", self.model_hf_file])
+        if self.models_dir:
+            server_args.extend(["--models-dir", self.models_dir])
+        if self.models_max is not None:
+            server_args.extend(["--models-max", self.models_max])
         if self.n_batch:
             server_args.extend(["--batch-size", self.n_batch])
         if self.n_ubatch:
@@ -204,6 +212,8 @@ class ServerProcess:
             server_args.extend(["--draft-min", self.draft_min])
         if self.no_webui:
             server_args.append("--no-webui")
+        if self.no_models_autoload:
+            server_args.append("--no-models-autoload")
         if self.jinja:
             server_args.append("--jinja")
         else:
@@ -295,7 +305,13 @@ class ServerProcess:
         result = ServerResponse()
         result.headers = dict(response.headers)
         result.status_code = response.status_code
-        result.body = response.json() if parse_body else None
+        if parse_body:
+            try:
+                result.body = response.json()
+            except JSONDecodeError:
+                result.body = response.text
+        else:
+            result.body = None
         print("Response from server", json.dumps(result.body, indent=2))
         return result
 
@@ -434,8 +450,9 @@ class ServerPreset:
     @staticmethod
     def tinyllama2() -> ServerProcess:
         server = ServerProcess()
-        server.model_hf_repo = "ggml-org/models"
-        server.model_hf_file = "tinyllamas/stories260K.gguf"
+        server.offline = True # will be downloaded by load_all()
+        server.model_hf_repo = "ggml-org/test-model-stories260K"
+        server.model_hf_file = None
         server.model_alias = "tinyllama-2"
         server.n_ctx = 512
         server.n_batch = 32
@@ -479,8 +496,8 @@ class ServerPreset:
     def tinyllama_infill() -> ServerProcess:
         server = ServerProcess()
         server.offline = True # will be downloaded by load_all()
-        server.model_hf_repo = "ggml-org/models"
-        server.model_hf_file = "tinyllamas/stories260K-infill.gguf"
+        server.model_hf_repo = "ggml-org/test-model-stories260K-infill"
+        server.model_hf_file = None
         server.model_alias = "tinyllama-infill"
         server.n_ctx = 2048
         server.n_batch = 1024
@@ -537,6 +554,7 @@ class ServerPreset:
     @staticmethod
     def router() -> ServerProcess:
         server = ServerProcess()
+        server.offline = True # will be downloaded by load_all()
         # router server has no models
         server.model_file = None
         server.model_alias = None