feat(settings): add generic OpenAI provider

[hsinchao-athena]

Description

Addresses the worker crash: Failed to extract accountId from token when using standard OpenAI API keys with the default "ChatGPT" platform connection.

Currently, the "ChatGPT" integration (chatgpt provider ID) is hardcoded to use the openai-codex engine from @mariozechner/pi-ai, which explicitly expects OAuth JWT Device-Code flow tokens. Supplying standard API keys (sk-...) causes a parsing error when the pi-ai library tries to extract the accountId.

This PR appends a new generic OpenAI provider configuration block to config/system-skills.json. This registers a distinct "OpenAI" connection option in the dashboard that safely routes to the standard openai provider slug in pi-ai ("sdkCompat": "openai"), bypassing the JWT decoding.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Performance improvement
• Refactoring

Testing

• Ran bun test and all tests pass
• Ran bun run format and bun run lint
• Verified changes work in Docker Compose (make dev)

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• Any dependent changes have been merged and published

Related Issues

Closes #(issue number)

Additional Notes

The system-skills.json patch adds the new generic provider while preserving all existing integrations.
(Note: bun run lint surfaced a few pre-existing a11y and key index warnings in packages/landing/... which are unrelated to this JSON patch).

[buremba]

Thanks for the contribution! This was a missing piece — we had no way for users to configure standard OpenAI API keys through the settings UI. Merged!