feat(techdemo): add opaque island bridge

Add a canvas leaf-widget island to the techdemo that receives server snapshots through Effect::event/CustomEvent while keeping slhx core and runtime semantics unchanged.

req: interop/001

req: examples/001

req: examples/005

examples/techdemo/src/main.rs

@@ -133,6 +133,7 @@ struct ControlCenter {
     board: SafeHtml,
     inspector: SafeHtml,
     activity: SafeHtml,
+    island_snapshot: String,
 }
 
 #[derive(Hemplate)]
@@ -207,6 +208,7 @@ async fn main() {
         .route("/slhx.js", get(runtime))
         .route("/app.css", get(app_css))
         .route("/control_center.css", get(control_center_css))
+        .route("/island.js", get(island_js))
         .with_state(state);
 
     let addr = std::env::var("SLHX_TECHDEMO_ADDR")
@@ -234,6 +236,7 @@ async fn architecture(request: PageRequest) -> impl IntoResponse {
         board: architecture_board(),
         inspector: architecture_inspector(),
         activity: architecture_activity(),
+        island_snapshot: "2|3|21|architecture route · same opaque island bridge".to_owned(),
     });
     request
         .page(body, shell)
@@ -253,6 +256,10 @@ async fn control_center_css() -> impl IntoResponse {
     ([("content-type", "text/css; charset=utf-8")], include_str!("../templates/control_center.css"))
 }
 
+async fn island_js() -> impl IntoResponse {
+    ([("content-type", "text/javascript; charset=utf-8")], include_str!("../templates/island.js"))
+}
+
 async fn interact(
     State(state): State<Arc<Shared>>,
     form: InteractionForm,
@@ -383,6 +390,7 @@ fn registry(shared: Arc<Shared>) -> HandlerRegistry {
                     }),
                     ui::control_center::slots::activity.render(&activity_view(&demo)),
                     ui::control_center::slots::notice.text("Push simulated · no client app code"),
+                    slhx::event("slhx:island-orbit", island_snapshot(&demo)),
                 )
             }
         })
@@ -413,6 +421,7 @@ fn demo_effects(demo: &DemoState, notice: &'static str) -> impl IntoEffect {
         ui::control_center::slots::inspector.render(&inspector_view(demo)),
         ui::control_center::slots::notice.text(notice),
         ui::control_center::forms::launch_work.clear("title"),
+        slhx::event("slhx:island-orbit", island_snapshot(demo)),
     )
 }
 
@@ -421,6 +430,23 @@ fn parse_lane(value: Option<&str>) -> usize {
     LANES.iter().position(|(id, _, _)| *id == value).unwrap_or(0)
 }
 
+fn island_snapshot(demo: &DemoState) -> String {
+    // Opaque leaf-widget bridge: compact server snapshot in, native CustomEvent out.
+    // req: interop/001 req: examples/001
+    let active = demo.work.iter().filter(|item| item.stage == Stage::Active).count();
+    let shipped = demo.work.iter().filter(|item| item.stage == Stage::Shipped).count();
+    let impact: u64 = demo.work.iter().map(|item| item.impact as u64).sum();
+    format!(
+        "{}|{}|{}|{} active · {} shipped · {} activity rows",
+        active + shipped,
+        demo.work.len(),
+        impact,
+        active,
+        shipped,
+        demo.activity.len()
+    )
+}
+
 fn page_html(demo: &DemoState) -> String {
     // Explicit full-page composition boundary for already-rendered hemplate fragments.
     // req: html_safety/002 req: view/001
@@ -429,6 +455,7 @@ fn page_html(demo: &DemoState) -> String {
         board: render_board(demo),
         inspector: render_inspector(demo),
         activity: render_activity(demo),
+        island_snapshot: island_snapshot(demo),
     })
 }