Release 2.9.3: switch primary to gpt-oss:120b-cloud with mistral vision fallback

- config: primary model → gpt-oss:120b-cloud (faster general chat, 2.72s median)
- server-v2: fix vision regex to exclude gpt-oss (gpt(?!-oss) negative lookahead)
  * gpt-oss was incorrectly matching /gpt/ → image data sent to non-vision model
  * applied at all 3 _supportsVision check sites (lines 5204, 6362, 7832)
- server-v2: vision fallback routing — when primary lacks vision support and user
  message contains images, automatically route to orchestration.secondary
  (mistral-large-3:675b-cloud, 4.27s avg, fastest vision cloud model)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.smallclaw/config.json

@@ -21,7 +21,7 @@
     "providers": {
       "ollama": {
         "endpoint": "http://localhost:11434",
-        "model": "gemini-3-flash-preview:cloud"
+        "model": "gpt-oss:120b-cloud"
       },
       "lm_studio": {
         "endpoint": "http://host.docker.internal:1234",
@@ -45,11 +45,11 @@
     }
   },
   "models": {
-    "primary": "gemini-3-flash-preview:cloud",
+    "primary": "gpt-oss:120b-cloud",
     "roles": {
-      "manager": "gemini-3-flash-preview:cloud",
-      "executor": "gemini-3-flash-preview:cloud",
-      "verifier": "gemini-3-flash-preview:cloud",
+      "manager": "gpt-oss:120b-cloud",
+      "executor": "gpt-oss:120b-cloud",
+      "verifier": "gpt-oss:120b-cloud",
       "background_task": ""
     }
   },