pi: default agent sessions to gpt-5.4 codex

Use the updated OpenAI Codex provider and model for new pi sessions.

Author: juanibiapina

dotfiles/pi/.pi/agent/settings.json

@@ -1,8 +1,8 @@
 {
   "lastChangelogVersion": "0.57.1",
   "theme": "tokyonight-moon",
-  "defaultProvider": "anthropic",
-  "defaultModel": "claude-opus-4-6",
+  "defaultProvider": "openai-codex",
+  "defaultModel": "gpt-5.4",
   "defaultThinkingLevel": "xhigh",
   "editorPaddingX": 1,
   "packages": [
@@ -18,7 +18,7 @@
   "enabledModels": [
     "anthropic/claude-opus-4-6:xhigh",
     "zai/glm-5:xhigh",
-    "openai-codex/gpt-5.3-codex:xhigh"
+    "openai-codex/gpt-5.4:xhigh"
   ],
   "doubleEscapeAction": "none",
   "terminal": {