feat: unify model selection and complete favorite settings

config/artemis.jsonc

@@ -2,12 +2,12 @@
 {
   "default": {
     "provider": "openai",
-    "model": "${env:OPENAI_MODEL:-mimo-v2.6-flash}",
+    "model": "${env:OPENAI_MODEL:-gpt-6-luna}",
     "timeout": "${env:OPENAI_TIMEOUT_SECONDS:-300}",
     "max_retries": "${env:OPENAI_MAX_RETRIES:-5}",
     "fallback": {
       "provider": "openai",
-      "model": "${env:OPENAI_MODEL:-mimo-v2.6-flash}"
+      "model": "${env:OPENAI_MODEL:-gpt-6-luna}"
     }
   },
   "presets": {},
@@ -52,7 +52,7 @@
       "explorer_mode": "flash",
       "step_summarizer": {
         "enabled": "${env:ARTEMIS_STEP_SUMMARIZER_ENABLED:-true}",
-        "model": "${env:OPENAI_MODEL:-mimo-v2.6-flash}",
+        "model": "${env:OPENAI_MODEL:-gpt-6-luna}",
         "timeout_seconds": "${env:ARTEMIS_STEP_SUMMARIZER_TIMEOUT_SECONDS:-120}",
         "prune_history_xml": true
       }
@@ -112,7 +112,7 @@
         "max_steps": 12,
         "min_steps": 6,
         "target_source_tokens": 6000,
-        "model": "${env:OPENAI_MODEL:-mimo-v2.6-flash}",
+        "model": "${env:OPENAI_MODEL:-gpt-6-luna}",
         "max_chunks": 8
       },
       "recall": {