Add resource SSR primitive, restore live demos in Examples section

- sx_primitives.ml: register resource as SSR stub returning signal
  {loading: true} — server renders loading state, client hydrates fetch
- reactive-islands/index.sx: Examples section with all 15 demo islands
  rendered inline alongside highlighted source code

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

hosts/ocaml/lib/sx_primitives.ml

@@ -686,6 +686,18 @@ let () =
        | None -> raise (Eval_error ("Store not found: " ^ name)))
     | _ -> raise (Eval_error "use-store: expected (name)"));
   register "clear-stores" (fun _args -> Hashtbl.clear store_registry; Nil);
+  (* resource — SSR stub: return signal with {loading: true}, client hydrates real fetch *)
+  register "resource" (fun _args ->
+    let state = Hashtbl.create 8 in
+    Hashtbl.replace state "loading" (Bool true);
+    Hashtbl.replace state "data" Nil;
+    Hashtbl.replace state "error" Nil;
+    let sig_d = Hashtbl.create 8 in
+    Hashtbl.replace sig_d "__signal" (Bool true);
+    Hashtbl.replace sig_d "value" (Dict state);
+    Hashtbl.replace sig_d "subscribers" (List []);
+    Hashtbl.replace sig_d "deps" (List []);
+    Dict sig_d);
   register "apply" (fun args ->
     let call f a =
       match f with

sx/sx/reactive-islands/index.sx

@@ -236,11 +236,12 @@
     (~docs/section
       :title "Examples"
       :id "examples"
-      (p "Source for every demo island on this page.")
+      (p "Each example below shows a live island and its source.")
       (~docs/section
         :title "Counter"
         :id "demo-counter"
         (p "Signals, computed, and " (code "swap!") ".")
+        (~reactive-islands/index/demo-counter :initial 0)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-counter")
@@ -252,6 +253,7 @@
           "Two signals, each derived from the other via "
           (code "effect")
           ".")
+        (~reactive-islands/index/demo-temperature)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-temperature")
@@ -260,6 +262,7 @@
         :title "Imperative Handlers"
         :id "demo-imperative"
         (p "Multi-statement " (code "(do ...)") " bodies in event handlers.")
+        (~reactive-islands/index/demo-imperative)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-imperative")
@@ -272,6 +275,7 @@
           " and "
           (code "clear-interval")
           " with signal-driven UI.")
+        (~reactive-islands/index/demo-stopwatch)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-stopwatch")
@@ -280,6 +284,7 @@
         :title "Reactive List"
         :id "demo-reactive-list"
         (p "Dynamic list with keyed reconciliation.")
+        (~reactive-islands/index/demo-reactive-list)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-reactive-list")
@@ -288,6 +293,7 @@
         :title "Input Binding"
         :id "demo-input-binding"
         (p "Two-way binding via " (code ":bind") " attribute.")
+        (~reactive-islands/index/demo-input-binding)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-input-binding")
@@ -299,6 +305,7 @@
           "Reactive class toggling with "
           (code "deref")
           " in attribute expressions.")
+        (~reactive-islands/index/demo-dynamic-class)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-dynamic-class")
@@ -307,6 +314,7 @@
         :title "Portal"
         :id "demo-portal"
         (p "Render content outside the island's DOM subtree.")
+        (~reactive-islands/index/demo-portal)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-portal")
@@ -315,6 +323,7 @@
         :title "Error Boundary"
         :id "demo-error-boundary"
         (p "Catch rendering errors without crashing the page.")
+        (~reactive-islands/index/demo-error-boundary)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-error-boundary")
@@ -323,6 +332,7 @@
         :title "DOM Refs"
         :id "demo-refs"
         (p "Access raw DOM elements via " (code ":ref") " signal.")
+        (~reactive-islands/index/demo-refs)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-refs")
@@ -334,6 +344,7 @@
           "Async data fetching with "
           (code "promise-then")
           " and loading state.")
+        (~reactive-islands/index/demo-resource)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-resource")
@@ -347,6 +358,7 @@
           " and "
           (code "batch")
           ".")
+        (~reactive-islands/index/demo-transition)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-transition")
@@ -360,10 +372,12 @@
           " / "
           (code "use-store")
           ".")
+        (~reactive-islands/index/demo-store-writer)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-store-writer")
             "lisp"))
+        (~reactive-islands/index/demo-store-reader)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-store-reader")
@@ -375,6 +389,7 @@
           "Server-rendered content communicating with an island via "
           (code "bridge-event")
           ".")
+        (~reactive-islands/index/demo-event-bridge)
         (~docs/code
           :src (highlight
             (component-source "~reactive-islands/index/demo-event-bridge")