fix(web): add rel=external to docs links to bypass SPA router

Leptos Router intercepts all <a> clicks for client-side navigation.
Docs links point to a static mdBook site outside the SPA, so the
router finds no matching route and renders NotFound. Adding
rel="external" tells the router to skip interception.

Author: 0xwonj

crates/tabula-web/src/layout/nav.rs

@@ -71,7 +71,7 @@ pub fn SiteNav() -> impl IntoView {
                 "tabula"
             </A>
             <div class="nav-links">
-                <a href=docs_href() class="nav-link">"Docs"</a>
+                <a href=docs_href() rel="external" class="nav-link">"Docs"</a>
                 <A href=app_href("/playground") attr:class="nav-link">"Playground"</A>
                 <button class="nav-theme-btn" on:click=toggle title="Toggle theme">
                     {move || if is_dark.get() { "\u{2600}" } else { "\u{263E}" }}

crates/tabula-web/src/pages/home/footer_cta.rs

@@ -18,7 +18,7 @@ pub fn FooterCta() -> impl IntoView {
             </div>
             <div class="cta-links">
                 <A href=app_href("/playground") attr:class="action filled">"Playground"</A>
-                <a href=docs_href() class="action ghost">"Documentation"</a>
+                <a href=docs_href() rel="external" class="action ghost">"Documentation"</a>
             </div>
         </section>
     }

crates/tabula-web/src/pages/home/hero.rs

@@ -16,7 +16,7 @@ pub fn HeroSection() -> impl IntoView {
             </p>
             <div class="hero-cta">
                 <A href=app_href("/playground") attr:class="action filled">"Playground"</A>
-                <a href=docs_href() class="action ghost">"Documentation"</a>
+                <a href=docs_href() rel="external" class="action ghost">"Documentation"</a>
             </div>
         </section>
     }

crates/tabula-web/src/pages/home/mod.rs

@@ -71,7 +71,7 @@ pub fn HomePage() -> impl IntoView {
                         <span class="paper-toc-dots" />
                         <span class="paper-toc-desc">"Try the DSL and prover"</span>
                     </A>
-                    <a href=docs_href() class="paper-toc-entry">
+                    <a href=docs_href() rel="external" class="paper-toc-entry">
                         <span class="paper-toc-num">"2."</span>
                         <span class="paper-toc-label">"Documentation"</span>
                         <span class="paper-toc-dots" />