feat(core): add gpt-5.3-codex model support (#9628)

* feat(core): add gpt-5.3-codex model support

Add OpenAI gpt-5.3-codex model: context window overrides, model pricing
and capabilities, none-reasoning-effort support, and test config.

🐾 Generated with [Letta Code](https://letta.com)

Co-Authored-By: Letta <noreply@letta.com>

* just stage-api && just publish-api

---------

Co-authored-by: Letta <noreply@letta.com>

tests/configs/llm_model_configs/openai-gpt-5.3-codex.json

@@ -0,0 +1,8 @@
+{
+  "context_window": 32000,
+  "model": "gpt-5.3-codex",
+  "model_endpoint_type": "openai",
+  "model_endpoint": "https://api.openai.com/v1",
+  "model_wrapper": null,
+  "reasoning_effort": "low"
+}