feat: add pstack-style rigor skill family for Zed

- wursor-precheck: router skill, entry point for non-trivial tasks
- wursor-principles: 21 engineering principles adapted for Wursor
- wursor-tdd, wursor-bug-fix, wursor-feature, wursor-investigation,
  wursor-review, wursor-decision-log: playbook skills
- AGENTS.md: repo guide wiring the skill routing table
- Fix: double-quote YAML frontmatter descriptions (colon-space in
  plain scalars broke Zed's skill loader)

AGENTS.md

@@ -0,0 +1,51 @@
+# Wursor — Agent Guide
+
+This repository is **Wursor**, the agentic WordPress management platform. Before starting any non-trivial task, read this file and follow the skill routing below.
+
+## The product, in one line
+
+Non-technical WordPress site owners describe what they want; Wursor makes it happen in a cloud sandbox, shows a live preview, and deploys on approval. The interface is chat → preview → approve. Nothing else.
+
+## Repo layout
+
+```
+api/               Node.js + TypeScript API server (session manager, agent orchestrator,
+                   playbook runner, sandbox manager, deploy manager, plugin client)
+web/               React + TypeScript frontend (chat, preview, approve/reject, deploy history)
+plugin/            WordPress plugin (PHP) — the connector on the user's hosting
+infrastructure/    Docker images, warm pool, GC, deploy scripts
+e2e/               Playwright end-to-end tests
+PRD.md             Product requirements (v2.0 — non-technical-first)
+IMPLEMENTATION.md  TDD build guide with 8-sprint Phase 1 plan
+```
+
+## Skill routing — use the precheck first
+
+The `.agents/skills/` directory is a family of rigor skills modeled on Cursor's pstack. **The entry point for any non-trivial task is `wursor-precheck`** — it routes to the right playbook and sets the verification bar.
+
+| Task shape | Skill |
+|---|---|
+| Any non-trivial task — start here | `wursor-precheck` |
+| How does X work / why was Y built this way | `wursor-investigation` |
+| A defect — reproduce, root-cause, fix | `wursor-bug-fix` |
+| New behavior, TDD-first from a data shape | `wursor-feature` |
+| Review a diff / PR across lenses | `wursor-review` |
+| Any code change with a test path | `wursor-tdd` |
+| Capture a reviewable decision trail | `wursor-decision-log` |
+| Structure, tradeoffs, verification standards | `wursor-principles` |
+
+## Hard rules
+
+1. **Tests first.** No implementation without a failing test (see `wursor-tdd`). Coverage floors: api/ + web/ ≥ 90%, plugin/ ≥ 80%.
+2. **Prove it works.** A task is not done on self-report — run the test, start the sandbox, hit the endpoint.
+3. **Non-technical-first.** The user never sees a diff, a terminal, a settings screen, or an error log. If a change would leak engineer-only UI into the product, it's wrong.
+4. **Safety.** Never touch a live WordPress site, production credentials, or real user data from this repo. Sandboxes are the only environment code runs against.
+5. **Decisions are logged.** Non-trivial choices get a decision-log entry (see `wursor-decision-log`).
+
+## Stack notes
+
+- Backend: Node.js + TypeScript, Express/Fastify, PostgreSQL (Wursor data), Redis (SSE/queue)
+- Frontend: React + TypeScript, Vite
+- Sandboxes: Docker on VPS, pre-baked WordPress image, overlayfs layers, media proxied (not copied)
+- Plugin: standard WordPress PHP plugin, REST API + token auth
+- Tests: vitest (api, web), phpunit (plugin), Playwright (e2e)