Authentication secrets instructions mismatch

Here... https://github.com/anthropics/claude-code-action/blob/02e9ed31816be8cb8d521a26f4ba981e5c89ac5e/examples/claude.yml#L37 only
anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }} is mentioned, but [setup guide](https://github.com/anthropics/claude-code-action/blob/main/docs/setup.md#manual-setup-direct-api) talks about
claude_code_oauth_token: ${{ secrets.CLAUDE_CODE_OAUTH_TOKEN }}

Possibly I would raise a mini PR like this... https://github.com/anthropics/claude-code-action/blob/02e9ed31816be8cb8d521a26f4ba981e5c89ac5e/docs/experimental.md?plain=1#L82

I am not sure this would be valid PR. If 'claude_code_oauth_token' can't be used there, then we should add comment sth like 'claude_code_oauth_token is not supported'., but that would then be misalligned with the [Manual setup guide](https://github.com/anthropics/claude-code-action/blob/main/docs/setup.md#manual-setup-direct-api).