feat(islands): wire islands end to end

The island pieces existed but nothing connected .wrn compilation to island
emission. Now:

- codegen emits a data-wrn-island placeholder for component tags bound to
  .tsx imports, keeping .wrn components on the normal mount path
- the dev pipeline and static build resolve island imports, thread the
  names into codegen, and build the bundles
- collectScripts adds /__wrnexus/islands.js only when island markup is
  present, so island-free pages still ship nothing
- island routes classify as static-interactive via hasIslands

Three bugs found by driving a real page in the browser:

1. The mount runtime was never built anywhere, so the bootstrap 404'd and
   no island mounted.
2. Building the runtime separately from the islands gave each its own copy
   of React: "Cannot read properties of null (reading 'useState')". The
   runtime is now an entrypoint of the same build so React stays in one
   shared chunk. The existing single-React test only compared bundles
   within one build and could not see across build boundaries.
3. Island props arrived as attribute strings, so start={3} was "3" and
   incrementing produced "31" then "311". Props now follow JSX semantics:
   {…} parses as JSON, quoted values stay strings, and a runtime
   expression is a WRN-ISLAND-PROPS build error rather than a silent
   wrong value.

island-codegen.ts no longer imports @wrnexus/core. Compiler modules are
bundled into the Node-only VS Code extension, which contains no other
packages, so a runtime import of core broke the editor compiler; the two
helpers are implemented locally and the core dependency is dropped again.

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

packages/dev-server/test/island-e2e.test.ts

@@ -0,0 +1,73 @@
+import { afterAll, expect, test } from "bun:test";
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import { compile, generate, islandNamesFrom, resolveWrnImports } from "@wrnexus/compiler";
+import { collectScripts } from "../src/script-selection.ts";
+
+const created: string[] = [];
+afterAll(() => {
+  for (const dir of created) rmSync(dir, { recursive: true, force: true });
+});
+
+function app() {
+  const root = mkdtempSync(join(process.cwd(), ".island-e2e-"));
+  created.push(root);
+  mkdirSync(join(root, "app"), { recursive: true });
+  writeFileSync(
+    join(root, "app", "Chart.tsx"),
+    `export default function Chart({ title }: { title: string }) { return <div>{title}</div>; }`,
+  );
+  writeFileSync(join(root, "app", "Card.wrn"), `component Card { view { <div>card</div> } }`);
+  return root;
+}
+
+test("a .wrn importing a .tsx emits an island marker and requests the bootstrap", () => {
+  const root = app();
+  const page = join(root, "app", "page.wrn");
+  const source = [
+    'import Chart from "./Chart"',
+    'import Card from "./Card"',
+    "page Home {",
+    "  view {",
+    '    <Chart title="Revenue" client:visible />',
+    "    <Card />",
+    "  }",
+    "}",
+  ].join("\n");
+  writeFileSync(page, source);
+
+  const ast = compile(source, page).ast;
+  const islands = islandNamesFrom(
+    resolveWrnImports(ast.structuredImports, page, { appRoot: root }),
+  );
+
+  // Only the .tsx import is an island; the .wrn component is not.
+  expect([...islands]).toEqual(["Chart"]);
+
+  const out = generate(ast, { islands });
+  expect(out).toContain('data-wrn-island="Chart"');
+  expect(out).toContain('data-wrn-island-strategy="visible"');
+  expect(out).toContain('data-component="Card"');
+
+  // Rendered island markup must pull in the island bootstrap.
+  expect(collectScripts('<div data-wrn-island="Chart"></div>')).toContain("/__wrnexus/islands.js");
+});
+
+test("a page with no .tsx imports emits no island markup and no island script", () => {
+  const root = app();
+  const page = join(root, "app", "plain.wrn");
+  const source = ['import Card from "./Card"', "page Plain {", "  view { <Card /> }", "}"].join(
+    "\n",
+  );
+  writeFileSync(page, source);
+
+  const ast = compile(source, page).ast;
+  const islands = islandNamesFrom(
+    resolveWrnImports(ast.structuredImports, page, { appRoot: root }),
+  );
+  expect(islands.size).toBe(0);
+
+  const out = generate(ast, { islands });
+  expect(out).not.toContain("data-wrn-island");
+  expect(collectScripts(out)).not.toContain("/__wrnexus/islands.js");
+});

packages/dev-server/test/island-scripts.test.ts

@@ -0,0 +1,16 @@
+import { expect, test } from "bun:test";
+import { collectScripts } from "../src/script-selection.ts";
+
+test("island markup pulls in the island bootstrap", () => {
+  const scripts = collectScripts(`<div data-wrn-island="Chart"></div>`);
+  expect(scripts).toContain("/__wrnexus/islands.js");
+});
+
+test("markup without islands ships no island bootstrap", () => {
+  expect(collectScripts(`<p>plain server html</p>`)).toEqual([]);
+});
+
+test("islands alone do not pull in the reactive runtime", () => {
+  const scripts = collectScripts(`<div data-wrn-island="Chart"></div>`);
+  expect(scripts).not.toContain("/__wrnexus/reactive.js");
+});

packages/dev-server/test/not-found-runtime.test.ts

@@ -22,7 +22,10 @@ function customNotFoundRuntime() {
     router: buildRouter(app),
     loadModule: async (file) =>
       file.includes(`${join("api", "404")}.ts`)
-        ? { GET: () => Response.json({ code: "CUSTOM_NOT_FOUND" }, { headers: { "x-custom": "yes" } }) }
+        ? {
+            GET: () =>
+              Response.json({ code: "CUSTOM_NOT_FOUND" }, { headers: { "x-custom": "yes" } }),
+          }
         : { default: () => "<main><h1>That page is gone</h1></main>" },
     getMiddleware: async () => [],
     assets: { serve: async () => null },