Test Python SDK against the built CLI and installed runtime (#44053)

## Why

Python SDK CI needs to exercise the checkout's CLI while retaining coverage of the wheel installation and its default runtime.

## What changed

- Run the Python SDK test suite against the same Bazel-built CLI as the TypeScript SDK tests. Build and stage `codex-code-mode-host` alongside the CLI so it can be discovered.
- Make the Python test harness prefer `CODEX_EXEC_PATH`, then a local debug build, then the installed runtime. Exclude optional turn-cost probes from recorded model requests.
- Add a separate installation job that builds the Python SDK wheel and installs it in a fresh environment.

## Testing

The installation smoke test verifies that imports resolve to the installed SDK and that its default runtime completes a mocked turn with the expected user input and final response.

GitOrigin-RevId: 8e3126742a014e2cf042afe799bc657e1ea2a282

sdk/python/tests/app_server_harness.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import json
+import os
 import queue
 import shutil
 import threading
@@ -204,7 +205,7 @@ class MockResponsesServer:
 
 
 class AppServerHarness:
-    """Test fixture that points a pinned runtime app-server at MockResponsesServer."""
+    """Test fixture that points the checkout's app-server at MockResponsesServer."""
 
     def __init__(self, tmp_path: Path, *, requires_openai_auth: bool = False) -> None:
         self.tmp_path = tmp_path
@@ -226,8 +227,14 @@ class AppServerHarness:
         shutil.rmtree(self.workspace, ignore_errors=True)
 
     def app_server_config(self) -> CodexConfig:
-        """Build SDK config for an isolated pinned-runtime app-server process."""
+        """Prefer the CI binary, then a local debug build, then the installed runtime."""
+        binary_name = "codex.exe" if os.name == "nt" else "codex"
+        debug_binary = Path(__file__).resolve().parents[3] / "codex-rs/target/debug" / binary_name
+        codex_bin = os.environ.get("CODEX_EXEC_PATH")
+        if codex_bin is None and debug_binary.is_file():
+            codex_bin = str(debug_binary)
         return CodexConfig(
+            codex_bin=codex_bin,
             cwd=str(self.workspace),
             env={
                 "CODEX_HOME": str(self.codex_home),
@@ -304,6 +311,10 @@ class _ResponsesHandler(BaseHTTPRequestHandler):
         """Serve queued SSE responses for `/v1/responses` requests."""
         length = int(self.headers.get("content-length", "0"))
         body = self.rfile.read(length)
+        if self.path.endswith("/analytics/codex/turn-costs"):
+            # Optional cost probes are not model requests.
+            self.send_error(404, "turn costs are unavailable for the mock provider")
+            return
         self.server.mock._record_request(self, body)
 
         if not (self.path.endswith("/v1/responses") or self.path.endswith("/responses")):

sdk/python/tests/installed_sdk_smoke.py

@@ -0,0 +1,34 @@
+"""Exercise a built SDK's default runtime in an otherwise isolated environment."""
+
+from dataclasses import replace
+from importlib.metadata import distribution, version
+from pathlib import Path
+from tempfile import TemporaryDirectory
+
+from app_server_harness import AppServerHarness
+
+import openai_codex
+from openai_codex import Codex
+
+
+def main() -> None:
+    installed_root = Path(distribution("openai-codex").locate_file("")).resolve()
+    assert Path(openai_codex.__file__).resolve().is_relative_to(installed_root), (
+        "The smoke test must import the installed SDK, not the source checkout"
+    )
+
+    with TemporaryDirectory() as directory, AppServerHarness(Path(directory)) as harness:
+        harness.responses.enqueue_assistant_message("Installed SDK works")
+        config = replace(harness.app_server_config(), codex_bin=None)
+        with Codex(config=config) as codex:
+            result = codex.thread_start().run("Check the installed SDK")
+        assert result.final_response == "Installed SDK works"
+        assert harness.responses.single_request().message_input_texts("user")[-1:] == [
+            "Check the installed SDK"
+        ]
+
+    print(f"Installed SDK passed with CLI runtime {version('openai-codex-cli-bin')}")
+
+
+if __name__ == "__main__":
+    main()