Fix hero-canvas navigation race; style the prosekit editor and add a toolbar

- Hero: gate RasterizedYES construction on a NodeRef resolving, not
  just "the Effect ran". Root cause of the reported "loading..." stall
  + "RefCell already borrowed" panic - navigating back to / client-side
  could run the Effect before the new <canvas> was actually in the
  DOM, yes.js did an unchecked getElementById(...).getContext() on
  null and threw mid-reactive-update, corrupting wasm_bindgen_futures'
  executor badly enough to panic on the next tick. Same NodeRef-gating
  pattern the prosekit editor's own mount already used.
- style/main.css: .prosekit-wrap/.prosekit-toolbar/.prosekit-editor to
  match the existing input/textarea look (border, background, focus
  ring).
- prosekit-editor.js: a real toolbar (Bold, Italic, H1, H2, Link, and
  a dedicated Gitea-repo-embed button reusing the paste rule's own
  insert logic) with active-state highlighting via the standard
  ProseMirror markActive/nodeActive idiom.

src/app.rs

@@ -232,11 +232,11 @@ fn Hero(title: String, description: String, show_yes: bool) -> impl IntoView {
     // Only the landing page gets the full interactive piece - it's the
     // one page this is actually "the" hero for; other pages (thank-you
     // pages, /review) get the plain dark header below. Starts the
-    // animation once the canvas elements exist (post-mount, via
-    // Effect), and explicitly stops the requestAnimationFrame loop on
-    // unmount - the original page-owning script never needed this since
-    // navigating away meant a full document unload, which doesn't
-    // happen in an SPA.
+    // animation once the canvas elements exist, and explicitly stops
+    // the requestAnimationFrame loop on unmount - the original
+    // page-owning script never needed this since navigating away meant
+    // a full document unload, which doesn't happen in an SPA.
+    let raster_ref: NodeRef<leptos::html::Canvas> = NodeRef::new();
     #[cfg(feature = "hydrate")]
     if show_yes {
         // `on_cleanup` requires Send + Sync (even single-threaded, wasm),
@@ -245,7 +245,21 @@ fn Hero(title: String, description: String, show_yes: bool) -> impl IntoView {
         // cnats' WebRTC call state uses for its own non-Send peer map).
         let instance: StoredValue<Option<yes::RasterizedYes>, LocalStorage> =
             StoredValue::new_local(None);
+        // Gated on the canvas NodeRef resolving, not just "the Effect
+        // ran" - on a fresh page load the DOM is already there by the
+        // time this fires, but navigating back to `/` client-side hit a
+        // real race: the Effect ran before the new view's <canvas> was
+        // actually inserted, RasterizedYES::new() (yes.js) did an
+        // unchecked `document.getElementById(...).getContext(...)` on
+        // null and threw mid-reactive-update - which then corrupted
+        // wasm_bindgen_futures' single-threaded executor state badly
+        // enough to panic ("RefCell already borrowed") on the next
+        // tick. Waiting for the NodeRef itself guarantees DOM presence
+        // the same way the prosekit editor's own mount Effect does.
         Effect::new(move |_| {
+            if raster_ref.get().is_none() {
+                return;
+            }
             instance.set_value(Some(yes::RasterizedYes::new()));
         });
         on_cleanup(move || {
@@ -264,7 +278,7 @@ fn Hero(title: String, description: String, show_yes: bool) -> impl IntoView {
                     view! {
                         <div class="hero-canvas" aria-hidden="true">
                             <canvas id="lineCanvas"></canvas>
-                            <canvas id="rasterCanvas"></canvas>
+                            <canvas id="rasterCanvas" node_ref=raster_ref></canvas>
                         </div>
                     }
                 })}
@@ -502,7 +516,7 @@ fn AlternativeCard(
                                                                 prop:value=move || sig.get()
                                                                 on:input=move |ev| sig.set(event_target_value(&ev))
                                                             />
-                                                            <div class="prosekit-editor" node_ref=container_ref></div>
+                                                            <div class="prosekit-wrap" node_ref=container_ref></div>
                                                         </label>
                                                     }
                                                     .into_any();