docs: add .agents workspace and the Astro refactor plan

Adds the agent-facing workspace and a 20-task plan for migrating the site
to Astro. Nothing here implements the refactor; these are briefs, rules and
templates that the task agents read.

- .agents/ holds context, rules, checklists, skills, specialist agents,
  component/page/config templates and gate scripts. It is vendor-neutral so
  MiniMax, Gemini and Codex can all read it; CLAUDE.md just points at
  AGENTS.md.
- .husky/ plus .lintstagedrc.json wire the three gate tiers. gate.sh locks on
  the shared git-common-dir so parallel worktrees serialise, and guards the
  assertion count in scripts/verify.mjs against a coverage drop.
- plans/astro-refactor/ carries the phase graph, per-task briefs and the
  model-routing recommendation.

These files must be tracked before fanning out: a worktree only checks out
tracked files, so an untracked plan is invisible to every agent working in one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

plans/astro-refactor/task-06-content-review.md

@@ -0,0 +1,43 @@
+# Task 06 — Review-desk content out of catalog.js
+
+**Agent**: `content-i18n-migrator` · **Model**: MiniMax-M3
+**Depends on**: 04 · **Parallel with**: 05 · **Blocks**: 16
+**Worktree**: `.agents/scripts/worktree.sh start 06 content-review`
+
+## Goal
+
+24 review entries become a typed collection, with the `improved` markdown as
+real `.md` files.
+
+## Scope
+
+`src/content/reviews/**`, `scripts/build-skill-review.mjs`.
+
+## Steps
+
+1. Move all 24 entries from `skills-review/catalog.js` (27 KB) and
+   `submitted-catalog.js` (18 KB) into the collection.
+2. `improved` becomes a real Markdown file per entry, rendered at build time.
+   That deletes the hand-rolled client-side renderer.
+3. **Re-point `scripts/build-skill-review.mjs`** at the collection.
+
+## The two traps
+
+1. **The generator writes committed files.**
+   `skill-reviews/improved/**/SKILL.md` is generated from the `improved` fields
+   and the output is in git. Move `catalog.js` and the generator keeps running
+   against nothing — **silently, exit code 0**. Prove it still produces
+   byte-identical output:
+   ```bash
+   node scripts/build-skill-review.mjs && git diff --exit-code skill-reviews/
+   ```
+2. **The diff view needs raw source.** The review desk compares original and
+   improved as *text*. If `improved` only exists as rendered HTML, the change
+   lens breaks. Keep the raw string reachable.
+
+## Done when
+
+- [ ] 24 entries in the collection; `verify.mjs`'s `id:'` count assertion still passes
+- [ ] `git diff --exit-code skill-reviews/` clean after regenerating
+- [ ] `astro check` passes
+- [ ] Every reference to the generator still accurate (`package.json`, `README.md`, `docs/operations-guide.md`, the review desk footer)