feat: add opt-in provider runtime abstraction

[celia-oai]

Summary

• Add codex-model-provider as the runtime home for model-provider behavior that does not belong in codex-core, codex-login, or codex-api.
• The new crate wraps configured ModelProviderInfo in a ModelProvider trait object that can resolve the API provider config, provider-scoped auth manager, and request auth provider for each call.
• This centralizes provider auth behavior in one place today, and gives us an extension point for future provider-specific auth, model listing, request setup, and related runtime behavior.

Tests

Ran tests manually to make sure that provider auth under different configs still work as expected.

[celia-oai]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

codex/codex-rs/core/src/codex.rs

Lines 1744 to 1746 in 4d9d09d

	let auth_env_telemetry = collect_auth_env_telemetry(
	&session_configuration.provider,
	auth_manager.codex_api_key_env_enabled(),

Use runtime auth source when building session telemetry

Session::new still builds auth-env telemetry from the legacy provider and base auth manager. When ProviderRuntime::Resolved is active, request auth can come from resolved auth state (env/static/command) and a different auth manager, so startup telemetry reports incorrect auth-env context and can mislead diagnostics.

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[celia-oai]

💡 Codex Review

codex/codex-rs/core/src/codex.rs

Lines 1744 to 1746 in 4d9d09d

	let auth_env_telemetry = collect_auth_env_telemetry(
	&session_configuration.provider,
	auth_manager.codex_api_key_env_enabled(),

Use runtime auth source when building session telemetry
Session::new still builds auth-env telemetry from the legacy provider and base auth manager. When ProviderRuntime::Resolved is active, request auth can come from resolved auth state (env/static/command) and a different auth manager, so startup telemetry reports incorrect auth-env context and can mislead diagnostics.

ℹ️ About Codex in GitHub

this seems to be a small tech debt. Cleaning it up as part of this PR.

[celia-oai]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Keep it up!

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[celia-oai]

@codex review