refactor: use @vercel/detect-agent for repo creation

[lihbr]

Description

• replace the manual AI harness detector with @vercel/detect-agent
• move repository creation agent detection into src/clients/wroom.ts
• remove the old shared detector and the tracking-side agent field added in feat(tracking): identify CLI and detect AI agent harness #175
• add a focused unit test for repository creation query params

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Note

Low Risk
Low risk refactor that swaps how the agent value is detected and reported during repository creation and telemetry; main risk is slightly different agent names/behavior affecting query params or tracking metadata.

Overview
Switches repository creation and telemetry agent detection to @vercel/detect-agent, removing the project’s custom environment-based detector.

createRepository now determines the agent internally (and only adds the agent query param when detection succeeds), and repo-create no longer passes an agent field. The old src/lib/ai.ts helper is deleted and package.json/package-lock.json are updated to include the new dev dependency.

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[angeloashmore]

💡 #idea: I prefer keeping the clients as a light layer above the API, essentially just a TypeScript wrapper around the endpoints. It helps keep the mental model simple in each area of the CLI.

That being said, I see the benefit of adding it in here.