2026-03-07 Stabilize experimental python SDK foundation

Description:
- pin datamodel-code-generator to an exact version and invoke it through the active interpreter
- make generate_types own the maintained generated surfaces and regenerate committed artifacts
- make sdk/python tests hermetic and regeneration checks idempotent

sdk/python/docs/getting-started.md

@@ -0,0 +1,75 @@
+# Getting Started
+
+This is the fastest path from install to a multi-turn thread using the minimal SDK surface.
+
+## 1) Install
+
+From repo root:
+
+```bash
+cd sdk/python
+python -m pip install -e .
+```
+
+Requirements:
+
+- Python `>=3.10`
+- bundled runtime binary for your platform (shipped in package)
+- Local Codex auth/session configured
+
+## 2) Run your first turn
+
+```python
+from codex_app_server import Codex, TextInput
+
+with Codex() as codex:
+    print("Server:", codex.metadata.server_name, codex.metadata.server_version)
+
+    thread = codex.thread_start(model="gpt-5")
+    result = thread.turn(TextInput("Say hello in one sentence.")).run()
+
+    print("Thread:", result.thread_id)
+    print("Turn:", result.turn_id)
+    print("Status:", result.status)
+    print("Text:", result.text)
+```
+
+What happened:
+
+- `Codex()` started and initialized `codex app-server`.
+- `thread_start(...)` created a thread.
+- `turn(...).run()` consumed events until `turn/completed` and returned a `TurnResult`.
+
+## 3) Continue the same thread (multi-turn)
+
+```python
+from codex_app_server import Codex, TextInput
+
+with Codex() as codex:
+    thread = codex.thread_start(model="gpt-5")
+
+    first = thread.turn(TextInput("Summarize Rust ownership in 2 bullets.")).run()
+    second = thread.turn(TextInput("Now explain it to a Python developer.")).run()
+
+    print("first:", first.text)
+    print("second:", second.text)
+```
+
+## 4) Resume an existing thread
+
+```python
+from codex_app_server import Codex, TextInput
+
+THREAD_ID = "thr_123"  # replace with a real id
+
+with Codex() as codex:
+    thread = codex.thread(THREAD_ID)
+    result = thread.turn(TextInput("Continue where we left off.")).run()
+    print(result.text)
+```
+
+## 5) Next stops
+
+- API surface and signatures: `docs/api-reference.md`
+- Common decisions/pitfalls: `docs/faq.md`
+- End-to-end runnable examples: `examples/README.md`