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-07-primitives.md

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+# Task 07 — Primitives
+
+**Agent**: `component-builder` · **Model**: MiniMax-M3 — **use this task to
+calibrate the model routing before fanning out**
+**Depends on**: 02 · **Blocks**: 08–11
+**Worktree**: `.agents/scripts/worktree.sh start 07 primitives`
+
+## Goal
+
+The four smallest reusable pieces, so the four parallel block tasks compose
+rather than reinvent.
+
+## Scope
+
+`src/components/primitives/` — `Eyebrow.astro`, `Rule.astro`, `Callout.astro`,
+`CodeBlock.astro`. Nothing else.
+
+## Why these four
+
+Each appears 10+ times across the current stylesheets:
+
+- **Eyebrow** — `10–11px` monospace, `letter-spacing:.08–.1em`, uppercase. The
+  single most repeated treatment on the site and a signature of the design.
+- **Rule** — the `border-top: 4px solid var(--gold)` section divider.
+- **Callout** — gold-background emphasis block (`.callout`, `.thesis`).
+- **CodeBlock** — `<pre>` on `--ink` with gold text.
+
+## Steps
+
+Copy `.agents/templates/components/static-block.astro` for each. Typed props,
+tokens only, zero JS. Then grep the current CSS for every place each treatment
+appears and confirm the component covers them all — if it needs five variants,
+you have found two components, not one.
+
+## Done when
+
+- [ ] `.agents/checklists/before-component.md` complete for all four
+- [ ] Rendered output visually identical to the CSS classes they replace
+- [ ] `npm run gate` green
+- [ ] **Routing note written**: how many iterations, what the model got wrong.
+      This decides whether 08–11 run on M3 or move to Codex.
+
+## Do not
+
+Do not build blocks or touch pages. Do not edit `tokens.css`.