fix(techdemo): rebootstrap inserted islands

Keep opaque island widgets live when slhx swaps or later DOM insertion adds a new island, and tear down the listener when an island leaves the document.

req: interop/001

req: examples/001

examples/techdemo/tests/browser_e2e.rs

@@ -52,6 +52,8 @@ async fn browser_drives_typed_product_end_to_end() -> WebDriverResult<()> {
         assert_text(&driver, "No selectors. Generated resources address every target.").await?;
         assert_text(&driver, "Opaque island bridge").await?;
         wait_for_runtime(&driver).await?;
+        insert_probe_island(&driver).await?;
+        wait_for_text(&driver, "#probe-island [data-island-readout]", "probe live").await?;
 
         driver
             .find(By::Css(&handle_selector(ui::control_center::handles::simulate_push)))
@@ -97,6 +99,7 @@ async fn browser_drives_typed_product_end_to_end() -> WebDriverResult<()> {
 
         driver.find(By::Css("a[href='/architecture']")).await?.click().await?;
         wait_for_text(&driver, &slot_selector(ui::control_center::slots::inspector), "Page swap").await?;
+        wait_for_text(&driver, "[data-island-readout]", "activity rows").await?;
         assert!(driver.current_url().await?.as_str().ends_with("/architecture"));
 
         driver.goto(&format!("http://{APP_ADDR}/")).await?;
@@ -133,6 +136,27 @@ fn card_button_selector(handle_id: impl std::fmt::Display, work_id: u64) -> Stri
     format!(r#"[data-hid="{handle_id}"][data-work-id="{work_id}"]"#)
 }
 
+async fn insert_probe_island(driver: &WebDriver) -> WebDriverResult<()> {
+    driver
+        .execute(
+            r#"
+            document.querySelector('[data-slhx-root]').insertAdjacentHTML('beforeend', `
+              <article id="probe-island" data-slhx-island="orbit" data-island-snapshot="1|1|1|probe waiting">
+                <canvas width="32" height="16"></canvas>
+                <p data-island-readout="">waiting</p>
+              </article>
+            `);
+            setTimeout(() => {
+              document.querySelector('[data-slhx-root]').dispatchEvent(new CustomEvent('slhx:island-orbit', { bubbles: true, detail: '7|2|8|probe live' }));
+            }, 25);
+            return true;
+            "#,
+            Vec::new(),
+        )
+        .await?;
+    Ok(())
+}
+
 async fn drag_card_to_lane(driver: &WebDriver, work_id: u64, lane: &str) -> WebDriverResult<()> {
     driver
         .execute(

examples/techdemo/tests/e2e.rs

@@ -71,6 +71,8 @@ fn product_is_e2e_working_over_http() {
     assert!(island.header("content-type").contains("javascript"));
     assert!(island.text().contains("slhx:island-orbit"));
     assert!(island.text().contains("data-slhx-island"));
+    assert!(island.text().contains("MutationObserver"));
+    assert!(island.text().contains("removeEventListener"));
 
     let architecture = request("GET", "/architecture", &[("X-SLHX-Partial", "1")], "");
     assert_eq!(architecture.status, 200);