Unified overrides for custom router and orchestrator models (#820)

* support configurable orchestrator model via orchestration config section

* add self-hosting docs and demo for Plano-Orchestrator

* list all Plano-Orchestrator model variants in docs

* use overrides for custom routing and orchestration model

* update docs

* update orchestrator model name

* rename arch provider to plano, use llm_routing_model and agent_orchestration_model

* regenerate rendered config reference

config/plano_config_schema.yaml

@@ -173,7 +173,7 @@ properties:
         provider_interface:
           type: string
           enum:
-            - arch
+            - plano
             - claude
             - deepseek
             - groq
@@ -220,7 +220,7 @@ properties:
         provider_interface:
           type: string
           enum:
-            - arch
+            - plano
             - claude
             - deepseek
             - groq
@@ -271,6 +271,12 @@ properties:
       upstream_tls_ca_path:
         type: string
         description: "Path to the trusted CA bundle for upstream TLS verification. Default is '/etc/ssl/certs/ca-certificates.crt'."
+      llm_routing_model:
+        type: string
+        description: "Model name for the LLM router (e.g., 'Arch-Router'). Must match a model in model_providers."
+      agent_orchestration_model:
+        type: string
+        description: "Model name for the agent orchestrator (e.g., 'Plano-Orchestrator'). Must match a model in model_providers."
   system_prompt:
     type: string
   prompt_targets:
@@ -408,14 +414,6 @@ properties:
     enum:
       - llm
       - prompt
-  routing:
-    type: object
-    properties:
-      llm_provider:
-        type: string
-      model:
-        type: string
-    additionalProperties: false
   state_storage:
     type: object
     properties: