feat: API server model name derived from profile name (#6857)

* feat: API server model name derived from profile name

For multi-user setups (e.g. OpenWebUI), each profile's API server now
advertises a distinct model name on /v1/models:

- Profile 'lucas' -> model ID 'lucas'
- Profile 'admin' -> model ID 'admin'
- Default profile -> 'hermes-agent' (unchanged)

Explicit override via API_SERVER_MODEL_NAME env var or
platforms.api_server.model_name config for custom names.

Resolves friction where OpenWebUI couldn't distinguish multiple
hermes-agent connections all advertising the same model name.

* docs: multi-user setup with profiles for API server + Open WebUI

- api-server.md: added Multi-User Setup section, API_SERVER_MODEL_NAME
  to config table, updated /v1/models description
- open-webui.md: added Multi-User Setup with Profiles section with
  step-by-step guide, updated model name references
- environment-variables.md: added API_SERVER_MODEL_NAME entry

tests/gateway/test_api_server.py

@@ -294,6 +294,40 @@ class TestModelsEndpoint:
             assert data["data"][0]["id"] == "hermes-agent"
             assert data["data"][0]["owned_by"] == "hermes"
 
+    @pytest.mark.asyncio
+    async def test_models_returns_profile_name(self):
+        """When running under a named profile, /v1/models advertises the profile name."""
+        with patch("gateway.platforms.api_server.APIServerAdapter._resolve_model_name", return_value="lucas"):
+            adapter = _make_adapter()
+        app = _create_app(adapter)
+        async with TestClient(TestServer(app)) as cli:
+            resp = await cli.get("/v1/models")
+            assert resp.status == 200
+            data = await resp.json()
+            assert data["data"][0]["id"] == "lucas"
+            assert data["data"][0]["root"] == "lucas"
+
+    @pytest.mark.asyncio
+    async def test_models_returns_explicit_model_name(self):
+        """Explicit model_name in config overrides profile name."""
+        extra = {"model_name": "my-custom-agent"}
+        config = PlatformConfig(enabled=True, extra=extra)
+        adapter = APIServerAdapter(config)
+        assert adapter._model_name == "my-custom-agent"
+
+    def test_resolve_model_name_explicit(self):
+        assert APIServerAdapter._resolve_model_name("my-bot") == "my-bot"
+
+    def test_resolve_model_name_default_profile(self):
+        """Default profile falls back to 'hermes-agent'."""
+        with patch("hermes_cli.profiles.get_active_profile_name", return_value="default"):
+            assert APIServerAdapter._resolve_model_name("") == "hermes-agent"
+
+    def test_resolve_model_name_named_profile(self):
+        """Named profile uses the profile name as model name."""
+        with patch("hermes_cli.profiles.get_active_profile_name", return_value="lucas"):
+            assert APIServerAdapter._resolve_model_name("") == "lucas"
+
     @pytest.mark.asyncio
     async def test_models_requires_auth(self, auth_adapter):
         app = _create_app(auth_adapter)