feat(tracking): identify CLI and detect AI agent harness

[angeloashmore]

Description

• Adds a detectAgent helper that identifies the AI coding agent (Claude Code, Codex, Cursor, Cline, Copilot, etc.) invoking the CLI based on environment variables. Groundwork for harness-aware tracking.
• createRepository now sends ?app=cli (and &agent=<harness> when detected) on POST /app/dashboard/repositories. On the API side (paired PR: prismicio/wroom#3189), app=cli maps to a new ExternalApp.CLI case so the Repository Created Segment event reports source=cli, and the agent query param is propagated as an agent trait on the same event.
• Prismic CLI Start and Prismic CLI End events now carry an agent property as well, so harness usage can be analyzed across the full CLI lifecycle, not only repo creation.

How to QA ¹

Deployed to dev-tools

• Use an agent to create a new repository with the CLI, initialize, etc:
  • PRISMIC_HOST=dev-tools-wroom.com npx prismic@pr-175 repo create -n my-repo
  • PRISMIC_HOST=dev-tools-wroom.com npx prismic@pr-175 init -r my-repo
• Check Segment live debugger to see the new source and agent properties

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Note

Low Risk
Low risk: adds a new standalone helper that only reads environment variables (and optionally checks a Linux file path) without changing existing execution paths.

Overview
Introduces src/lib/ai.ts with a new async detectAgent() helper that identifies the active AI agent by checking a prioritized set of environment variables (Claude Code/Cowork, Codex, Cursor, Cline, Copilot, etc.).

On Linux it additionally probes for a Devin marker at file:///opt/.devin, and it returns unknown-sandbox when IS_SANDBOX=yes.

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