[7/8] Add Python SDK app-server integration harness (#22014)

## Why

The SDK had behavioral tests that replaced SDK client internals. Those
tests could catch wrapper mistakes, but they did not prove the pinned
app-server runtime, generated notification models, request routing, and
sync/async public clients worked together.

This PR adds deterministic integration coverage that starts the pinned
`codex app-server` process and mocks only the upstream Responses HTTP
boundary.

## What

- Add `AppServerHarness` and `MockResponsesServer` helpers for isolated
`CODEX_HOME`, mock-provider config, queued SSE responses, and captured
`/v1/responses` requests.
- Add shared helpers for SSE construction, stream assertions,
approval-policy inspection, and image fixtures.
- Split integration coverage into focused modules for run behavior,
inputs, streaming, turn controls, approvals, and thread lifecycle.
- Cover sync and async `Thread.run`, `TurnHandle.stream`, interleaved
streams, approval-mode persistence, lifecycle helpers, final-answer
phase handling, image inputs, loaded skill input injection, steering,
interruption, listing, history reads, run overrides, and token usage
mapping.
- Replace public-wrapper tests that duplicated integration-test behavior
with lower-level client tests only where direct client behavior is the
thing under test.

## Stack

1. #21891 `[1/8]` Pin Python SDK runtime dependency
2. #21893 `[2/8]` Generate Python SDK types from pinned runtime
3. #21895 `[3/8]` Run Python SDK tests in CI
4. #21896 `[4/8]` Define Python SDK public API surface
5. #21905 `[5/8]` Rename Python SDK package to `openai-codex`
6. #21910 `[6/8]` Add high-level Python SDK approval mode
7. This PR `[7/8]` Add Python SDK app-server integration harness
8. #22021 `[8/8]` Add Python SDK Ruff formatting

## Verification

- Added pinned app-server integration tests under
`sdk/python/tests/test_app_server_*.py` and
`test_real_app_server_integration.py`.

---------

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

sdk/python/tests/test_client_rpc_methods.py

@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 from pathlib import Path
-from typing import Any
 
 from openai_codex.client import AppServerClient, _params_dict
 from openai_codex.generated.notification_registry import notification_turn_id
@@ -19,23 +18,6 @@ from openai_codex.models import Notification, UnknownNotification
 ROOT = Path(__file__).resolve().parents[1]
 
 
-def test_thread_set_name_and_compact_use_current_rpc_methods() -> None:
-    client = AppServerClient()
-    calls: list[tuple[str, dict[str, Any] | None]] = []
-
-    def fake_request(method: str, params, *, response_model):  # type: ignore[no-untyped-def]
-        calls.append((method, params))
-        return response_model.model_validate({})
-
-    client.request = fake_request  # type: ignore[method-assign]
-
-    client.thread_set_name("thread-1", "sdk-name")
-    client.thread_compact("thread-1")
-
-    assert calls[0][0] == "thread/name/set"
-    assert calls[1][0] == "thread/compact/start"
-
-
 def test_generated_params_models_are_snake_case_and_dump_by_alias() -> None:
     params = ThreadListParams(search_term="needle", limit=5)