Rename .pi to .feynman, rename citation agent to verifier, add website, skills, and docs

- Rename project config dir from .pi/ to .feynman/ (Pi supports this via piConfig.configDir)
- Rename citation agent to verifier across all prompts, agents, skills, and docs
- Add website with homepage and 24 doc pages (Astro + Tailwind)
- Add skills for all workflows (deep-research, lit, review, audit, replicate, compare, draft, autoresearch, watch, jobs, session-log, agentcomputer)
- Add Pi-native prompt frontmatter (args, section, topLevelCli) and read at runtime
- Remove sync-docs generation layer — docs are standalone
- Remove metadata/prompts.mjs and metadata/packages.mjs — not needed at runtime
- Rewrite README and homepage copy
- Add environment selection to /replicate before executing
- Add prompts/delegate.md and AGENTS.md

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

website/src/components/Nav.astro

@@ -0,0 +1,26 @@
+---
+import ThemeToggle from './ThemeToggle.astro';
+
+interface Props {
+  active?: 'home' | 'docs';
+}
+
+const { active = 'home' } = Astro.props;
+---
+
+<nav class="sticky top-0 z-50 bg-bg">
+  <div class="max-w-6xl mx-auto px-6 h-14 flex items-center justify-between">
+    <a href="/" class="text-xl font-bold text-accent tracking-tight">Feynman</a>
+    <div class="flex items-center gap-6">
+      <a href="/docs/getting-started/installation"
+        class:list={["text-sm transition-colors", active === 'docs' ? 'text-text-primary' : 'text-text-muted hover:text-text-primary']}>
+        Docs
+      </a>
+      <a href="https://github.com/getcompanion-ai/feynman" target="_blank" rel="noopener"
+        class="text-sm text-text-muted hover:text-text-primary transition-colors">
+        GitHub
+      </a>
+      <ThemeToggle />
+    </div>
+  </div>
+</nav>