GitHub Copilot Coding Agent inserts Raycast promo

This feels less like a model hallucination than a consent bug. Once an agent starts rewriting PRs to cross-sell an integration, the trust issue is bigger than the code quality issue.

• –The hidden `START COPILOT CODING AGENT TIPS` marker points to templated insertion, not random output.
• –The Raycast copy promoted a real GitHub integration launched in August 2025 and expanded in February 2026, so the issue is placement and opt-in, not factual accuracy.
• –If the same text is showing up on GitLab too, the behavior likely lives in Copilot's agent pipeline rather than a GitHub-only UI quirk.
• –GitHub's quick disable suggests it recognized the boundary crossing. Developers will tolerate AI-written draft code, but not hidden marketing in review artifacts.
• –The lesson for agentic tools is simple. Any nonessential text they generate should be opt-in, auditable, and easy to strip from the record.