pstack: refresh the docs and add a docs-vs-tree check

[poteto]

This brings the pstack README and guide in line with the current tree. It also adds a script that finds the next drift.

Stale claims fixed

• The README said Cursor ships a built-in /babysit. Cursor now ships /autopilot.
• The README and the overnight page said autopilot-full runs a full verifier swarm on every later push. The playbook runs the full swarm on the code-ready head. After that, a rebase or a small fix gets one fresh verifier, and only new behavior or a large diff gets the full swarm again.
• The README said that in Custom Mode, poteto-mode decides on its own when to apply, and that you can opt out by saying so. Neither the skill nor the Cursor docs back that. Both Custom Mode links now go straight to the Custom Mode section of the skills docs.
• The README listed the files that make the Claude Code tree go stale. That list grew when the tree started to copy the README and the guide, so the README now says to run the generator after any pstack change, and that the copy includes the README and the guide.
• The poteto-mode page said autopilot runs a PR queue. It also runs a stack.

Check script

node scripts/check-pstack-docs.mjs lists the skills, slash commands, playbooks, and agents in the tree and compares them with what the docs name. It also checks relative links, anchors, whole-set counts, and model names. On main it finds one problem, the /babysit claim. On this branch it finds none. CI does not run it yet.

Prose pass

Each guide page already keeps to one Diátaxis mode, so no page was split. The prose commit makes only sentence-level edits. It removes idioms, metaphors, comma splices, and mid-sentence colons, and it changes no claims.

The Claude Code tree copies the README and the guide, so one commit regenerates those copies. validate-plugins.mjs and generate-pstack-harness-trees.mjs --check pass.

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Note

Low Risk
Changes are limited to documentation and a validation script; no runtime product or auth paths are modified.

Overview
This PR refreshes pstack documentation so the README and guide match the current skills tree, and adds scripts/check-pstack-docs.mjs to catch future drift (slash commands, links/anchors, inventory counts, README tables, model names).

Accuracy fixes include replacing the stale built-in /babysit claim with /autopilot, tightening autopilot-full verifier behavior (full swarm on code-ready head; lighter checks on small follow-up pushes), simplifying Custom Mode wording and linking to the official anchor, and broadening harness regen instructions now that the Claude copy includes the README and guide.

The guide gets a sentence-level prose pass (no structural Diátaxis changes). The new checker is not wired into CI yet (per PR description).

^{Reviewed by Cursor Bugbot for commit 339f8ba. Bugbot is set up for automated code reviews on this repo. Configure here.}