Add Windows + WSL2 smoke tests for Codex Desktop thread start/resume regressions

Problem

The current Codex Desktop Stable 26.820.x regression breaks starting and resuming WSL-hosted threads with:

failed to load configuration: invalid transport in `mcp_servers.codex_app`

This is already tracked in #40819 and #40715.

The concerning part is that this regression appears to affect a basic, high-value workflow:

• Windows 11
• WSL2 workspace
• Codex Desktop configured to run the agent in WSL
• start a new thread
• resume an existing thread

A minimal smoke test covering this path should have failed immediately before the Stable release shipped.

Request

Please add release-gating regression coverage for the Codex Desktop -> WSL execution path, at minimum:

1. Launch Codex Desktop on Windows with WSL2 enabled.
2. Open a repository stored inside the WSL filesystem.
3. Start a new Codex thread in the WSL agent environment.
4. Resume an existing WSL-hosted thread.
5. Verify that Desktop-managed MCP configuration is valid and contains a usable transport before it is passed to the WSL app-server.
6. Verify that a failure caused by Desktop-generated runtime configuration does not incorrectly tell the user to fix config.toml.

Why this matters

For users who intentionally keep their repositories and toolchains inside WSL, switching the agent environment to Windows native is not an equivalent workaround. A regression in the Desktop -> WSL launch path can completely block development work.

The current incident also produced a misleading error message pointing at the user's config.toml, even though reports indicate the invalid mcp_servers.codex_app entry is generated by Desktop at runtime.

Expected outcome

A Stable release should not ship if basic Windows + WSL2 thread start/resume smoke tests fail. Please add automated or release-check coverage for this path so regressions like #40819 are caught before rollout.

Start by locating the Codex Desktop to WSL launch path and the code that generates Desktop-managed MCP runtime configuration. Exercise the Windows 11 and WSL2 workflow for opening a WSL repository, starting a thread, and resuming one. Done means release-gating coverage catches invalid transport configuration and does not blame the user's config.toml.