refactor(website): split Landing.vue into section components

Extract 2002-line monolith into landing/ subfolder:
- 8 section components (FolioHeader, HeroSection, ForgettingSection, AnatomySection, DialectSection, MechanicsSection, InstallSection, CatalogFooter)
- useLandingEffects.js composable for all vanilla-JS effects
- landing.css for all styles
- Landing.vue reduced to 28-line orchestrator

Also restores upstream hero lede text ("permanent. Designed for total recall.").

website/.vitepress/theme/landing/HeroSection.vue

@@ -0,0 +1,81 @@
+<template>
+  <section v-pre class="hero" id="hero">
+    <span class="corner-ticks" aria-hidden="true"><span></span></span>
+
+    <div class="hero-inner">
+      <div class="hero-copy">
+        <h1 class="display">
+          <span class="line">Memory is</span>
+          <span class="line line-2">identity.</span>
+        </h1>
+        <p class="lede">
+          An AI that forgets cannot know you. MemPalace keeps every word you have
+          shared — verbatim, on your machine, permanent. Designed for total
+          recall.
+        </p>
+        <form class="waitlist waitlist-hero" data-source="hero" novalidate>
+          <div class="waitlist-head">
+            <span class="waitlist-pulse" aria-hidden="true"></span>
+            <span class="waitlist-eyebrow">Subscribe for updates</span>
+          </div>
+          <div class="waitlist-row">
+            <input
+              type="email"
+              class="waitlist-input"
+              name="email"
+              placeholder="you@example.com"
+              autocomplete="email"
+              aria-label="Email address"
+              required
+            />
+            <button type="submit" class="waitlist-submit">
+              <span class="waitlist-label-default">Join the list</span>
+              <span class="waitlist-label-pending" aria-hidden="true">Joining…</span>
+              <svg class="waitlist-arrow" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.6" aria-hidden="true">
+                <path d="M5 12h14M13 6l6 6-6 6"/>
+              </svg>
+              <svg class="waitlist-check" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" aria-hidden="true">
+                <path d="M5 12l5 5 9-11"/>
+              </svg>
+            </button>
+          </div>
+          <p class="waitlist-msg" aria-live="polite"></p>
+        </form>
+
+        <div class="hero-secondary">
+          <a href="/guide/getting-started">Read the docs</a>
+          <span class="sep" aria-hidden="true">·</span>
+          <a href="https://github.com/MemPalace/mempalace">GitHub ↗</a>
+        </div>
+      </div>
+
+      <!-- Palace video visual -->
+      <div class="palace-stage" aria-hidden="true">
+        <div class="halo"></div>
+
+        <div class="stars">
+          <i style="top:12%; left:22%;  --t:5s;   --d:0.0s"></i>
+          <i style="top:18%; left:74%;  --t:6s;   --d:1.2s"></i>
+          <i style="top:34%; left:8%;   --t:4s;   --d:0.6s"></i>
+          <i style="top:44%; left:88%;  --t:7s;   --d:0.3s"></i>
+          <i style="top:62%; left:14%;  --t:5.5s; --d:1.8s"></i>
+          <i style="top:72%; left:82%;  --t:4.5s; --d:0.9s"></i>
+          <i style="top:82%; left:38%;  --t:6.2s; --d:2.4s"></i>
+          <i style="top:28%; left:52%;  --t:5.2s; --d:3.0s"></i>
+          <i style="top:88%; left:60%;  --t:4.8s; --d:1.5s"></i>
+          <i style="top:6%;  left:48%;  --t:6.8s; --d:0.4s"></i>
+        </div>
+
+        <video
+          class="palace-video"
+          src="/hero_video.mp4"
+          autoplay
+          muted
+          loop
+          playsinline
+          disablepictureinpicture
+        ></video>
+      </div>
+    </div>
+  </section>
+</template>