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/06_thread_lifecycle_and_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 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"})
+    first = thread.turn(TextInput("One sentence about structured planning.")).run()
+    second = thread.turn(TextInput("Now restate it for a junior engineer.")).run()
+
+    reopened = codex.thread_resume(thread.id)
+    listing_active = codex.thread_list(limit=20, archived=False)
+    reading = reopened.read(include_turns=True)
+
+    _ = reopened.set_name("sdk-lifecycle-demo")
+    _ = codex.thread_archive(reopened.id)
+    listing_archived = codex.thread_list(limit=20, archived=True)
+    unarchived = codex.thread_unarchive(reopened.id)
+
+    resumed_info = "n/a"
+    try:
+        resumed = codex.thread_resume(
+            unarchived.id,
+            model="gpt-5.4",
+            config={"model_reasoning_effort": "high"},
+        )
+        resumed_result = resumed.turn(TextInput("Continue in one short sentence.")).run()
+        resumed_info = f"{resumed_result.id} {resumed_result.status}"
+    except Exception as exc:
+        resumed_info = f"skipped({type(exc).__name__})"
+
+    forked_info = "n/a"
+    try:
+        forked = codex.thread_fork(unarchived.id, model="gpt-5.4")
+        forked_result = forked.turn(TextInput("Take a different angle in one short sentence.")).run()
+        forked_info = f"{forked_result.id} {forked_result.status}"
+    except Exception as exc:
+        forked_info = f"skipped({type(exc).__name__})"
+
+    compact_info = "sent"
+    try:
+        _ = unarchived.compact()
+    except Exception as exc:
+        compact_info = f"skipped({type(exc).__name__})"
+
+    print("Lifecycle OK:", thread.id)
+    print("first:", first.id, first.status)
+    print("second:", second.id, second.status)
+    print("read.turns:", len(reading.thread.turns or []))
+    print("list.active:", len(listing_active.data))
+    print("list.archived:", len(listing_archived.data))
+    print("resumed:", resumed_info)
+    print("forked:", forked_info)
+    print("compact:", compact_info)