Codex App: make Pull Requests navigation provider-agnostic and configurable

What variant of Codex are you using?

Codex App 26.707.72221 on macOS.

What feature would you like to see?

The top-level Pull Requests navigation in Codex App should be provider-agnostic and configurable instead of being hard-wired to GitHub and the gh CLI.

Many enterprise users work in local Git repositories backed by an internal or self-hosted SCM. For those users, a permanent Pull Requests item whose implementation assumes GitHub is not useful. It also makes a generic Git workflow appear dependent on one hosting vendor, even when the actual merge-request workflow is handled through another CLI, MCP server, or plugin.

Please support:

1. A configurable SCM provider interface for pull/merge request context:

• detect providers from Git remote URLs;
• allow built-in and custom providers;
• allow a CLI, MCP server, or plugin adapter to resolve the current branch to its pull/merge request;
• let providers define terminology such as "Pull Request" or "Merge Request".

1. An option to hide or disable the Pull Requests navigation when no supported provider is configured.
2. Scope gh discovery and authentication to the GitHub provider instead of treating it as a general prerequisite for this navigation.

Expected behavior

• Local Git, diff, branch review, and uncommitted-change review remain provider-agnostic.
• Selecting the Pull Requests navigation delegates to the configured provider.
• Non-GitHub repositories do not show GitHub-specific authentication or availability states.
• Users who do not use any hosted review workflow can remove the unused navigation item.

Why this matters

Codex already supports extensibility through CLIs, MCP servers, plugins, and skills. The pull/merge request surface should use the same model instead of coupling the product navigation to a single SCM vendor.

Related issues:

• openai/codex#30038 covers configurable Git providers and credentials.
• openai/codex#26963 covers GitLab merge-request links.
• openai/codex#29849 covers hiding GitHub PR status in non-GitHub workspaces.

This request focuses specifically on making the top-level Pull Requests navigation and its provider contract configurable, so enterprise and self-hosted SCM integrations can participate without requiring GitHub or gh.