feat(console-web): add bounded iframe keep-alive

- opt service and settings pages into document retention
- preserve iframe identity and local Solid state across navigation
- cap retained documents with deterministic LRU eviction
- deliver activate, deactivate, and dispose lifecycle messages
- reject commands emitted by inactive page documents
- expose page activity as a Solid accessor
- test retention, recreation, eviction, and invalid limits

crates/wasmeld-console/web/src/primitives/create-frame-bridge.ts

@@ -6,12 +6,13 @@ import { notifyReady, sendCommand } from "../sdk/page";
 /**
  * Connects one iframe document to the persistent Host Shell.
  *
- * The listener and state belong to the iframe's Solid owner. Navigating or
- * removing the iframe runs `onCleanup`, so the old document cannot continue to
- * receive Host snapshots.
+ * A keep-alive document remains mounted while inactive and exposes that state
+ * through `active`. Removing the iframe still runs `onCleanup`, so an evicted
+ * document cannot continue to receive Host snapshots.
  */
 export function createFrameBridge(view: View) {
   const [state, setState] = createSignal<HostSharedState | null>(null);
+  const [active, setActive] = createSignal(false);
 
   const receive = (event: MessageEvent<unknown>) => {
     if (event.origin !== window.location.origin || event.source !== window.parent) return;
@@ -19,8 +20,15 @@ export function createFrameBridge(view: View) {
     if (event.data.type === "state" && event.data.state.view === view) {
       setState(event.data.state);
     }
-    if (event.data.type === "dispose") {
-      window.dispatchEvent(new Event("wasmeld:dispose"));
+    if (event.data.type === "lifecycle") {
+      const phase = event.data.phase;
+      setActive(phase === "activate");
+      window.dispatchEvent(
+        new CustomEvent("wasmeld:lifecycle", {
+          detail: { phase },
+        }),
+      );
+      window.dispatchEvent(new Event(`wasmeld:${phase}`));
     }
   };
 
@@ -33,6 +41,7 @@ export function createFrameBridge(view: View) {
 
   return {
     state,
+    active,
     command(command: PageCommand) {
       sendCommand(view, command);
     },