Add Python SDK public API and examples

Co-authored-by: Codex <noreply@openai.com>

sdk/python/examples/05_existing_thread/async.py

@@ -0,0 +1,32 @@
+import sys
+from pathlib import Path
+
+_EXAMPLES_ROOT = Path(__file__).resolve().parents[1]
+if str(_EXAMPLES_ROOT) not in sys.path:
+    sys.path.insert(0, str(_EXAMPLES_ROOT))
+
+from _bootstrap import ensure_local_sdk_src, runtime_config
+
+ensure_local_sdk_src()
+
+import asyncio
+
+from codex_app_server import AsyncCodex, TextInput
+
+
+async def main() -> None:
+    async with AsyncCodex(config=runtime_config()) as codex:
+        original = await codex.thread_start(model="gpt-5", config={"model_reasoning_effort": "high"})
+
+        first_turn = await original.turn(TextInput("Tell me one fact about Saturn."))
+        first = await first_turn.run()
+        print("Created thread:", first.thread_id)
+
+        resumed = await codex.thread_resume(first.thread_id)
+        second_turn = await resumed.turn(TextInput("Continue with one more fact."))
+        second = await second_turn.run()
+        print(second.text)
+
+
+if __name__ == "__main__":
+    asyncio.run(main())