feat: add a built-in Amazon Bedrock model provider

[celia-oai]

Why

Codex needs a first-class amazon-bedrock model provider so users can select Bedrock without copying a full provider definition into config.toml. The provider has Codex-owned defaults for the pieces that should stay consistent across users: the display name, Bedrock base_url, and wire_api.

At the same time, users still need a way to choose the AWS credential profile used by their local environment. This change makes amazon-bedrock a partially modifiable built-in provider: code owns the provider identity and endpoint defaults, while user config can set model_providers.amazon-bedrock.aws.profile.

For example:

model_provider = "amazon-bedrock"

[model_providers.amazon-bedrock.aws]
profile = "codex-bedrock"

What Changed

• Added amazon-bedrock to the built-in model provider map with:
  • name = "Amazon Bedrock"
  • base_url = "https://bedrock-mantle.us-east-1.api.aws/v1"
  • wire_api = "responses"
• Added AWS provider auth config with a profile-only shape: model_providers.<id>.aws.profile.
• Kept AWS auth config restricted to amazon-bedrock; custom providers that set aws are rejected.
• Allowed model_providers.amazon-bedrock through reserved-provider validation so it can act as a partial override.
• During config loading, only aws.profile is copied from the user-provided amazon-bedrock entry onto the built-in provider. Other Bedrock provider fields remain hard-coded by the built-in definition.
• Updated the generated config schema for the new provider AWS profile config.

[celia-oai]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: b666344306

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".