pstack Adds /poteto-help Skill for Discovery

This is a small but important usability upgrade: workflow systems fail when users cannot discover the right entry point.

• –`/poteto-help` turns pstack’s documentation into an interactive router instead of forcing developers to memorize commands.
• –It complements `/poteto-mode`, which handles non-trivial work by selecting playbooks and invoking specialized skills.
• –The update improves onboarding but adds another layer that must stay aligned with rapidly changing skills and guides.
• –pstack remains most compelling for teams that want AI coding agents to investigate, design, implement, review, and verify systematically.