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/scripts/extract-strings.mjs

@@ -0,0 +1,45 @@
+#!/usr/bin/env node
+// Mechanically extract every { en, pt } string pair from a file or directory,
+// sorted and normalised, so a content migration can be proven lossless:
+//
+//   node .agents/scripts/extract-strings.mjs app.js       > /tmp/before.json
+//   node .agents/scripts/extract-strings.mjs src/content/ > /tmp/after.json
+//   diff /tmp/before.json /tmp/after.json
+//
+// A non-empty diff means you altered content. These are hand-written
+// translations with deliberate tone — copy them, never retype them.
+
+import { readdirSync, readFileSync, statSync } from 'node:fs';
+import { join } from 'node:path';
+
+const target = process.argv[2];
+if (!target) {
+  console.error('usage: extract-strings.mjs <file|dir>');
+  process.exit(2);
+}
+
+const walk = (dir) =>
+  readdirSync(dir).flatMap((name) => {
+    const path = join(dir, name);
+    return statSync(path).isDirectory() ? walk(path) : [path];
+  });
+
+const files = statSync(target).isDirectory() ? walk(target) : [target];
+
+// Matches `en: '…'` / "en": "…" and the pt counterpart, single or double quoted,
+// tolerating escaped quotes inside.
+const PAIR = /["']?\b(en|pt)\b["']?\s*:\s*(['"])((?:\\.|(?!\2)[\s\S])*)\2/g;
+
+const strings = [];
+for (const file of files) {
+  const source = readFileSync(file, 'utf8');
+  for (const match of source.matchAll(PAIR)) {
+    strings.push({ lang: match[1], value: match[3] });
+  }
+}
+
+// Sort so file ordering and structure changes do not show up as content changes.
+strings.sort((a, b) => (a.lang + a.value).localeCompare(b.lang + b.value));
+
+console.log(JSON.stringify(strings, null, 2));
+console.error(`extracted ${strings.length} strings from ${files.length} file(s)`);