Switch pi defaults to OpenAI API provider

- set pi default provider to openai for API key auth
- stop writing openai-codex into auth.json

Tests: manual
- pi -p --provider openai --model gpt-5.2-codex "ping"
- pi -p --provider anthropic --model claude-opus-4-5 "ping"

clawdinator/pi-settings.json

@@ -1,9 +1,9 @@
 {
-  "defaultProvider": "openai-codex",
+  "defaultProvider": "openai",
   "defaultModel": "gpt-5.2-codex",
   "defaultThinkingLevel": "xhigh",
   "enabledModels": [
-    "openai-codex/gpt-5.2-codex",
+    "openai/gpt-5.2-codex",
     "anthropic/claude-opus-4-5"
   ]
 }

scripts/pi-auth.sh

@@ -40,7 +40,6 @@ jq -n \
   --arg anthropic "$anthropic_key" \
   '{
     openai: { type: "api_key", key: $openai },
-    "openai-codex": { type: "api_key", key: $openai },
     anthropic: { type: "api_key", key: $anthropic }
   }' > "$tmp_file"