feat: sync upstream pstack (6 playbooks, /bro + 3 skills, official guide) - #9

Summary

Brings the tour back in sync with cursor/plugins/pstack, which has grown a lot since the last sync, and adds a section for the guide upstream now ships at pstack/docs/guide.

New in PLAYBOOKS (all from poteto-mode/SKILL.md), inserted where upstream lists them so neighbours that need contrasting stay adjacent: Babysit and Shipping (the two halves of getting a stack merged), Orchestrate, Autopilot-full, Autopilot-stack (next to Autonomous run, which they're easy to confuse with), and Worktree and simulator cleanup. Count copy goes 17 → 23 playbooks, 19 → 23 skills.

New in SKILLS: /bro, /swarm, /no-comments, /technical-writing. New MODELS roles from setup-pstack: hardest tasks, arena cross-judge pool, swarm workers.

KEYWORDS gained a set per new playbook. The risk there is stealing phrases from existing sets — "land the stack" is in the Run-overnight example chip, "migration across" belongs to multi-phase-plan — so every existing example chip was re-checked to confirm it still routes to the same playbook it did before, plus a spot check that each new playbook now matches its own phrasing.

The Guide section is markup, not data: ten a.chip cards linking the upstream chapters. .chip was written for <button>, so anchors needed one added rule to drop the inherited underline and keep the accent title / dim description split.

llms-full.txt is generated from the inline data by .github/scripts/generate.py, so it picks the above up automatically; the two hardcoded "Twenty principles" / "Twenty rules" strings in the generator were wrong (there are 21) and are fixed, and the generator + llms.txt now point agents at the guide index. changelog.json and the workflows are untouched.

Link to Devin session: https://app.devin.ai/sessions/96d44aa4c51a44ccbb461c5809e05726
Requested by: @HustleCoding