evert: remove experimental my.dash.board PWA virtual host

Reverts the experimental feature that attempted to serve the dashboard
via a local HTTP server registered as a hardcoded `my.dash.board` virtual
host, intended to satisfy Chrome's PWA "secure origin" installability
requirement. The approach caused proxy connection errors and file-not-found
issues that were not worth resolving.

Removed: native-host/dashboard-server.js, native-host/test-chain.mjs
Reverted: startup.js, message-router.js, virtual-hosts.js, index.js,
          build-distributable.js, extension/pages/virtual-hosts.js,
          CI workflows (ci.yml, release.yml)

native-host/holesail-manager/virtual-hosts.js

@@ -129,29 +129,6 @@ async function setVirtualHost(payload) {
   }
 }
 
-/**
- * Register a built-in local virtual host that is served by an internal HTTP
- * server rather than a Holesail P2P tunnel. The entry is marked `type: 'local'`
- * so it is never persisted to state.json and cannot be removed by the user.
- * @param {string} hostname - The hostname (e.g. `my.dash.board`).
- * @param {number} localPort - The local port the internal server is listening on.
- */
-function setLocalVirtualHost(hostname, localPort) {
-  virtualHosts.set(hostname, {
-    hostname,
-    hsUrl: null,
-    holesail: null,
-    localHost: TUNNEL_HOST,
-    localPort,
-    state: 'ready',
-    type: 'local',
-    createdAt: Date.now(),
-    reconnectTimer: null,
-    reconnectDelay: 0
-  });
-  debugLog('setLocalVirtualHost: hostname=', hostname, 'localPort=', localPort);
-}
-
 /**
  * Remove a virtual host, close its tunnel, and release its local port.
  * @param {object} payload
@@ -163,7 +140,6 @@ async function removeVirtualHost(payload) {
   debugLog('removeVirtualHost: hostname=', hostname);
   const entry = virtualHosts.get(hostname);
   if (!entry) return { ok: false, error: 'Virtual host not found' };
-  if (entry.type === 'local') return { ok: false, error: 'Built-in host cannot be removed' };
   if (entry.reconnectTimer) { clearTimeout(entry.reconnectTimer); entry.reconnectTimer = null; }
   if (entry.localPort) releaseTunnelPort(entry.localPort);
   if (entry.holesail) { try { await entry.holesail.close(); } catch (_) {} }
@@ -229,4 +205,4 @@ async function cleanupVirtualHosts() {
   virtualHosts.clear();
 }
 
-module.exports = { init, setVirtualHost, setLocalVirtualHost, removeVirtualHost, getVirtualHosts, getLocalPortForHostname, getLocalBackend, getVirtualHostMap, cleanupVirtualHosts, RECONNECT_BASE_MS, RECONNECT_MAX_MS };
+module.exports = { init, setVirtualHost, removeVirtualHost, getVirtualHosts, getLocalPortForHostname, getLocalBackend, getVirtualHostMap, cleanupVirtualHosts, RECONNECT_BASE_MS, RECONNECT_MAX_MS };