Update default main model to Claude Sonnet 5

Set the bundled model config, Balance preset, and onboarding OpenRouter default to anthropic/claude-sonnet-5. Refresh the model config README example to match.

plugins/_model_config/README.md

@@ -67,7 +67,7 @@ The project preset file uses the same plain YAML list schema as global presets.
 - name: Research
   chat:
     provider: openrouter
-    name: anthropic/claude-sonnet-4.6
+    name: anthropic/claude-sonnet-5
     api_base: ""
     ctx_length: 200000
     ctx_history: 0.7

plugins/_model_config/default_config.yaml

@@ -2,7 +2,7 @@ allow_chat_override: true
 
 chat_model:
   provider: "openrouter"
-  name: "anthropic/claude-sonnet-4.6"
+  name: "anthropic/claude-sonnet-5"
   api_base: ""
   ctx_length: 200000
   ctx_history: 0.7
@@ -30,4 +30,4 @@ embedding_model:
   api_base: ""
   rl_requests: 0
   rl_input: 0
-  kwargs: {}
+  kwargs: {}

plugins/_model_config/default_presets.yaml

@@ -13,7 +13,7 @@
 - name: "Balance"
   chat:
     provider: "openrouter"
-    name: "anthropic/claude-sonnet-4.6"
+    name: "anthropic/claude-sonnet-5"
     api_key: ""
     api_base: ""
     ctx_length: 200000

plugins/_onboarding/webui/onboarding-providers.js

@@ -213,7 +213,7 @@ export const ONBOARDING_PROVIDER_OVERRIDES = {
     setup_url: "https://openrouter.ai/",
     api_key_url: "https://openrouter.ai/workspaces/default/keys",
     docs_url: "https://openrouter.ai/workspaces/default/keys",
-    default_chat_model: "anthropic/claude-sonnet-4.6",
+    default_chat_model: "anthropic/claude-sonnet-5",
     default_utility_model: "google/gemini-3.1-flash-lite-preview",
     api_key_mode: "required",
     model_list_autoload: true,