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-10-guide-blocks.md

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+# Task 10 — Full-guide blocks
+
+**Agent**: `component-builder` · **Model**: MiniMax-M3
+**Depends on**: 07 · **Parallel with**: 08, 09, 11 · **Blocks**: 15
+**Worktree**: `.agents/scripts/worktree.sh start 10 guide-blocks`
+
+## Goal
+
+The full guide's distinctive sections as components — **static shells only**.
+Task 15 wires the interactivity.
+
+## Scope
+
+`src/components/blocks/` — `PhasePanel.astro`, `FleetDiagram.astro`,
+`HandoffTable.astro`, `WorktreeMap.astro`, `RouteTable.astro`,
+`SkillPackage.astro`.
+
+## Source
+
+`full-guide/index.html` (22 KB) + `styles.css` + `responsive.css`.
+
+## Critical: the `data-*` hooks are asserted by name
+
+`verify.mjs` requires these survive: `data-phase="plan|build|review"`,
+`data-tree="main|ui"`, `data-worker="ui"`, `data-route="plan"`,
+`data-model-provider="openai|claude|gemini"`, `data-effort="low|medium|high"`,
+`data-skill-file="skill"`, `data-skill-step="observe|validate"`,
+`data-common-skill="ponytail|caveman|unlazy"`, `role="tablist"`, `id="hands-on"`.
+
+Each is a real feature hook, not decoration. Losing one is losing a feature.
+
+## Watch for
+
+`responsive.css` is 30 KB of append-only overrides on top of `styles.css`. **Do
+not port it wholesale.** Take what each component needs, then prove the rest is
+dead. Expect to delete most of it — that is a win, not a risk, provided the
+screenshots agree.
+
+## Done when
+
+- [ ] Every `data-*` hook above present in rendered output
+- [ ] Components take props and render static markup; **no `client:*` yet**
+- [ ] Screenshots match the current guide at four widths
+- [ ] Checklist complete; `npm run gate` green