Add Python SDK public API and examples (#14446)

## TL;DR
WIP esp the examples

Thin the Python SDK public surface so the wrapper layer returns
canonical app-server generated models directly.

- keeps `Codex` / `AsyncCodex` / `Thread` / `Turn` and input helpers,
but removes alias-only type layers and custom result models
- `metadata` now returns `InitializeResponse` and `run()` returns the
generated app-server `Turn`
- updates docs, examples, notebook, and tests to use canonical generated
types and regenerates `v2_all.py` against current schema
- keeps the pinned runtime-package integration flow and real integration
coverage

  ## Validation
  - `PYTHONPATH=sdk/python/src python3 -m pytest sdk/python/tests`
- `GH_TOKEN="$(gh auth token)" RUN_REAL_CODEX_TESTS=1
PYTHONPATH=sdk/python/src python3 -m pytest sdk/python/tests -rs`

---------

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

sdk/python/examples/14_turn_controls/sync.py

@@ -0,0 +1,63 @@
+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 (
+    assistant_text_from_turn,
+    ensure_local_sdk_src,
+    runtime_config,
+)
+
+ensure_local_sdk_src()
+
+from codex_app_server import Codex, TextInput
+
+with Codex(config=runtime_config()) as codex:
+    thread = codex.thread_start(model="gpt-5.4", config={"model_reasoning_effort": "high"})
+    steer_turn = thread.turn(TextInput("Count from 1 to 40 with commas, then one summary sentence."))
+    steer_result = "sent"
+    try:
+        _ = steer_turn.steer(TextInput("Keep it brief and stop after 10 numbers."))
+    except Exception as exc:
+        steer_result = f"skipped {type(exc).__name__}"
+
+    steer_event_count = 0
+    steer_completed_status = "unknown"
+    steer_completed_turn = None
+    for event in steer_turn.stream():
+        steer_event_count += 1
+        if event.method == "turn/completed":
+            steer_completed_turn = event.payload.turn
+            steer_completed_status = getattr(event.payload.turn.status, "value", str(event.payload.turn.status))
+
+    steer_preview = assistant_text_from_turn(steer_completed_turn).strip() or "[no assistant text]"
+
+    interrupt_turn = thread.turn(TextInput("Count from 1 to 200 with commas, then one summary sentence."))
+    interrupt_result = "sent"
+    try:
+        _ = interrupt_turn.interrupt()
+    except Exception as exc:
+        interrupt_result = f"skipped {type(exc).__name__}"
+
+    interrupt_event_count = 0
+    interrupt_completed_status = "unknown"
+    interrupt_completed_turn = None
+    for event in interrupt_turn.stream():
+        interrupt_event_count += 1
+        if event.method == "turn/completed":
+            interrupt_completed_turn = event.payload.turn
+            interrupt_completed_status = getattr(event.payload.turn.status, "value", str(event.payload.turn.status))
+
+    interrupt_preview = assistant_text_from_turn(interrupt_completed_turn).strip() or "[no assistant text]"
+
+    print("steer.result:", steer_result)
+    print("steer.final.status:", steer_completed_status)
+    print("steer.events.count:", steer_event_count)
+    print("steer.assistant.preview:", steer_preview)
+    print("interrupt.result:", interrupt_result)
+    print("interrupt.final.status:", interrupt_completed_status)
+    print("interrupt.events.count:", interrupt_event_count)
+    print("interrupt.assistant.preview:", interrupt_preview)