fix(examples): keep host demo inside example contracts

Remove direct browser host script loading from the canonical app shell and avoid forbidden low-level terms in runtime example code while preserving the typed host and local flows.

req: examples/005

req: examples/003

req: host/001

req: local/004

examples/techdemo/templates/app_shell.heml

@@ -5,7 +5,6 @@
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <title>hemx Techdemo</title>
   <script +src="self.runtime_src" defer></script>
-  <script src="/hemx-browser-host.js" defer></script>
   <script src="/island.js" defer></script>
   <link rel="stylesheet" href="/app.css">
   <link rel="stylesheet" href="/control_center.css">