fix(islands): rebuild on .tsx edits and support islands inside components

Three bugs found by driving the dev server rather than reading code:

1. An island used inside a .wrn component still emitted a component mount
   — only the page and nested-page render paths were covered.

2. Editing an island .tsx never rebuilt in dev. The bundle cache was keyed
   on source path alone, and page modules are cached after the first
   request so no compile runs to notice the change. The cache key now
   includes mtime, and the file watcher rebuilds islands whose .tsx
   changed.

3. A .wrn cache hit skipped island building entirely, so after a restart
   with a warm cache no island bundle was ever produced. Island inputs are
   now persisted beside the other artifacts and rebuilt on a cache hit.

The islands manifest is deliberately excluded from the artifact
completeness check: only the async compile path writes it, so requiring it
made the sync path miss the cache on every call.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/dev-server/src/index.ts

@@ -43,6 +43,7 @@ import {
   loadWrnServerModule,
   setCompileCacheDir,
   setCompileImportOptions,
+  rebuildChangedIslands,
   setDevCompilerPipeline,
   wrnBrowserArtifactUrlAsync,
 } from "./pipeline.ts";
@@ -685,6 +686,18 @@ export async function startServer(opts: ServeOptions): Promise<RunningServer> {
 
       console.log(`[wrnexus] hot update — ${files.join(", ")}`);
       await pluginRunner.hook("hmrUpdate", files);
+      // Island .tsx sources are not .wrn files, so nothing below would rebuild
+      // them; page modules are cached, so no compile runs on the next request.
+      const islandFiles = files
+        .map((changed) => (isAbsolute(changed) ? changed : resolve(appDir, changed)))
+        .filter((changed) => changed.endsWith(".tsx"));
+      if (islandFiles.length > 0) {
+        try {
+          await rebuildChangedIslands(islandFiles);
+        } catch (error) {
+          console.warn("[wrnexus] island rebuild failed", error);
+        }
+      }
       const storeUpdates: Array<{ name: string; url: string; kind: string }> = [];
       for (const changed of files) {
         const absolute = isAbsolute(changed) ? changed : resolve(appDir, changed);