[am-will]

Oli has already prepared the plugin package. This PR fixes two things:

• Attachment handling: The instructions could tell ChatGPT to use an upload tool it doesn’t have. They now ask for a document link when the attachment can’t be passed through.
• ZIP contents: The builder previously included almost everything in the plugin folder. It now includes only reviewed files, with checks for credentials and local configuration.

Seven automated tests, GitHub CI, package validation and a local Codex install pass. The actual ChatGPT workflow still needs testing with a reviewer account.

Before submission, we still need OpenAI organization and domain verification, a reviewer account, a demo video, and product/privacy review of restricted-data handling.

The PR also includes a short handoff covering what’s been checked and what Oli still needs before submission.

Nothing has been submitted or deployed.