chore: remove Dark Provenance book references (book shelved)

The Dark Provenance book is shelved for now. Per Scott: remove the book
reference, keep the dark provenance idea.

This commit removes the book artifact references — the cards, the waitlist
CTAs, the Book schema entry, the SharedForm waitlist message — but does
not touch the underlying concept. The 'dark provenance' idea continues
to live in:
- /blog/the-taste-problem (dark-factory series post #5)
- /blog/spec-first-audit-surface (existing)
- the Speckl project card on /about
- the Speckl knowsAbout / project references in the SEO schema

Cover SVG at public/images/book-cover-dark-provenance.svg is intentionally
kept; un-shelving the book is a one-line restore across the four pages
when Scott calls it back.

Removed:
- src/pages/books.astro: full 'Dark Provenance' coming-soon card with
  cover, waitlist CTA, and mailto link
- src/pages/index.astro: 'Dark Provenance' book card on homepage
- src/pages/about.astro: 'Dark Provenance' book card in published-books grid
- src/components/SEO.astro: @type: Book schema entry
- src/components/Form/SharedForm.astro: 'we'll let you know when Dark
  Provenance is available' waitlist success message (was unreachable; form
  is only rendered with type=speaking or type=contact)

Build: 40 pages, 2.8s, clean. No remaining 'Dark Provenance' string in src/.

src/components/Form/SharedForm.astro

@@ -120,7 +120,7 @@ const topicParam = Astro.url.searchParams.get('topic');
 
   <div class="form-success" style="display:none;">
     <h4>{type === 'waitlist' ? "You're on the waitlist!" : 'Thanks for reaching out!'}</h4>
-    <p>{type === 'speaking' ? "Your inquiry has been submitted. Scott typically responds within 24 hours." : type === 'contact' ? "Your message has been submitted. Scott typically responds within 24 hours." : "We'll let you know when Dark Provenance is available."}</p>
+    <p>{type === 'speaking' ? "Your inquiry has been submitted. Scott typically responds within 24 hours." : "Your message has been submitted. Scott typically responds within 24 hours."}</p>
   </div>
 </div>
 

src/components/SEO.astro

@@ -234,19 +234,6 @@ function getJsonLd(pageType: string): string {
           description: 'Three questions that change how people learn. The simplest mentoring framework you\'ll actually use.',
           sameAs: 'https://a.co/d/0bRKZeUV',
         },
-        {
-          '@context': 'https://schema.org',
-          '@type': 'Book',
-          name: 'Dark Provenance',
-          author: {
-            '@type': 'Person',
-            name: 'Scott Scoble',
-            url: siteUrl,
-          },
-          datePublished: '2026',
-          bookFormat: 'https://schema.org/EBook',
-          description: 'Formal verification for the AI age. How to audit what your AI actually did.',
-        },
       ], null, 2);
 
     case 'consulting':

src/pages/about.astro

@@ -70,11 +70,6 @@ import BaseLayout from '../layouts/BaseLayout.astro';
           <p>Three questions that change how people learn.</p>
         </article>
 
-        <article class="book-card">
-          <h3>Dark Provenance</h3>
-          <p class="book-status">Coming 2026</p>
-          <p>Formal verification for the AI age. How to audit what your AI actually did.</p>
-        </article>
       </div>
     </div>
   </section>

src/pages/books.astro

@@ -49,19 +49,6 @@ import SharedForm from '../components/Form/SharedForm.astro';
           </div>
         </article>
 
-        <article class="book-card coming-soon">
-          <div class="book-cover">
-            <img src="/images/book-cover-dark-provenance.svg" alt="Dark Provenance book cover" width="150" height="225" loading="lazy" />
-          </div>
-          <h2>Dark Provenance</h2>
-          <p class="book-meta">Coming 2026</p>
-          <p class="book-description">Formal verification for the AI age. How to audit what your AI actually did.</p>
-          <p class="book-quote">"Speckl — the compile-time provenance layer. A new approach to AI accountability."</p>
-          
-          <p class="waitlist-info">Want early access? Email Scott directly to join the waitlist.</p>
-          <a href="mailto:scott@scoble.me?subject=Dark%20Provenance%20Interest" class="waitlist-btn">Email for Early Access</a>
-        </article>
-
       </div>
     </div>
   </section>

src/pages/index.astro

@@ -139,16 +139,6 @@ import NewsletterSignup from '../components/NewsletterSignup.astro';
         </div>
       </article>
 
-      <article class="book-card">
-        <div class="book-cover">
-          <img src="/images/book-cover-dark-provenance.svg" alt="Dark Provenance book cover" width="120" height="180" loading="lazy" />
-        </div>
-        <div class="book-info">
-          <h3>Dark Provenance</h3>
-          <p class="book-desc">Formal verification for the AI age. How to audit what your AI actually did. Coming 2026.</p>
-          <a href="https://www.amazon.com/stores/Scott-Scoble/author/B0GKSSBDMK" class="book-cta" target="_blank" rel="noopener" data-umami-event="home-book-author-amazon">More on Amazon →</a>
-        </div>
-      </article>
     </div>
   </section>