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>

.agents/templates/components/static-block.astro

@@ -0,0 +1,74 @@
+---
+// Static block template — the default. Ships zero JavaScript.
+// Copy to src/components/blocks/<Name>.astro and replace everything marked TODO.
+//
+// Before using this, confirm the block earns extraction: it appears three times,
+// or it has a name a person says out loud. See .agents/rules/componentization.md
+
+interface Props {
+  /** TODO: describe each prop. Required by default; optional needs a reason. */
+  eyebrow: string;
+  title: string;
+  body: string;
+  href?: string;
+}
+
+const { eyebrow, title, body, href } = Astro.props;
+---
+
+<article class="block">
+  <span class="eyebrow">{eyebrow}</span>
+  <h2>{title}</h2>
+  <p>{body}</p>
+  {href && <a href={href}>Open →</a>}
+  <slot />
+</article>
+
+<style>
+  /* Tokens only. No raw hex, no px font sizes, no ad-hoc breakpoints.
+     .agents/scripts/check-tokens.mjs enforces this. */
+  .block {
+    display: grid;
+    gap: 10px;
+    padding: 22px;
+    background: var(--paper);
+    color: var(--ink);
+  }
+
+  /* The house eyebrow: uppercase monospace, wide tracking. One class, not
+     fifteen repetitions. */
+  .eyebrow {
+    color: var(--accent);
+    font: var(--font-eyebrow);
+    letter-spacing: .1em;
+    text-transform: uppercase;
+  }
+
+  h2 {
+    margin: 0;
+    font-size: var(--step-5);
+    line-height: 1.05;
+    letter-spacing: -.06em; /* tight display tracking is a signature of this design */
+  }
+
+  p {
+    margin: 0;
+    color: var(--muted);
+    line-height: 1.65;
+  }
+
+  a {
+    color: var(--blue);
+    font-weight: 700;
+    text-decoration: none;
+  }
+
+  a:focus-visible {
+    outline: 3px solid var(--red);
+    outline-offset: 2px;
+  }
+
+  @media (max-width: 800px) {
+    .block { padding: 18px; }
+  }
+</style>