docs: clarify bedrock inference profile setup

[anduimagui]

Issue for this PR

Closes #

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

This updates the Bedrock docs to make the custom application inference profile flow explicit instead of just mentioning that the model id can be an ARN.

It adds a fuller opencode.json example, calls out that the custom model key should still look Claude-like for caching, and documents the practical AWS flow of creating the application profile from the matching system-defined inference profile when Bedrock rejects the raw foundation model ARN.

How did you verify your code works?

I verified the examples against a real Bedrock setup locally:

• created an application inference profile with AWS CLI
• confirmed the profile was ACTIVE
• invoked it successfully with aws bedrock-runtime converse
• checked that opencode debug config and opencode models amazon-bedrock picked up the custom model config

Screenshots / recordings

If this is a UI change, please include a screenshot or recording.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search results, I found the following potentially related PR:

Related PR:

• PR docs(web): clarify Amazon Bedrock setup #18880: docs(web): clarify Amazon Bedrock setup
  • This is an earlier documentation PR about clarifying Bedrock setup, which may cover similar ground or could benefit from the updated inference profile documentation in PR docs: clarify bedrock inference profile setup #24193.

The other result (PR #16504: feat(bedrock): add prompt caching support for custom ARNs) is a feature PR rather than documentation and addresses a different aspect of Bedrock integration.

These are related but not exact duplicates—PR #18880 is an older docs update while #24193 is the current PR you're reviewing with more specific inference profile setup guidance.

[github-actions]

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