feat(pwa): add PWA install support and update installation docs

Add manifest.webmanifest to the dashboard so Chrome can install it as
a standalone app via the browser menu. Register the manifest in
web_accessible_resources and link it from dashboard.html. Add a
dedicated PWA install section to docs/INSTALLATION.md covering install
steps, uninstall, and the requirement that the extension remains
installed.

docs/INSTALLATION.md

@@ -129,6 +129,28 @@ Self-hosted signing (without a public AMO listing) is available via the [AMO Dev
 
 ---
 
+## Installing the dashboard as a standalone app (PWA)
+
+The dashboard supports being installed as a standalone desktop app via Chrome's PWA install feature. This opens the dashboard in its own OS window without any browser chrome (no address bar, tabs, or toolbar).
+
+**Requirements:** The Holesail Browser extension must already be installed. The PWA is a launcher only — all functionality still runs through the extension and native host.
+
+### How to install
+
+1. Open the dashboard (click the Holesail icon in the toolbar, or press `Alt+Shift+H`)
+2. In Chrome, open the browser menu (**⋮** top right) → **Save and share** → **Install page as app**
+3. Confirm the install prompt — the dashboard will appear in your OS app launcher and dock
+
+Once installed, you can open Holesail directly from your desktop without opening a browser tab first.
+
+### Uninstalling the PWA
+
+In Chrome, go to `chrome://apps`, right-click **Holesail Browser**, and select **Remove from Chrome**. This removes the standalone app shortcut but does not affect the extension itself.
+
+> **Note:** The PWA requires the extension to remain installed. If you uninstall the extension, the installed app will no longer function.
+
+---
+
 ## First-time setup
 
 After loading the extension:

extension/dashboard/dashboard.html

@@ -7,6 +7,7 @@
   <link rel="preconnect" href="https://fonts.googleapis.com">
   <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
   <link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=JetBrains+Mono:wght@400;500&display=swap" rel="stylesheet">
+  <link rel="manifest" href="manifest.webmanifest">
   <link rel="stylesheet" href="../vendor/xterm.css">
   <link rel="stylesheet" href="dashboard.css">
   <script src="../vendor/xterm.js"></script>

extension/dashboard/manifest.webmanifest

@@ -0,0 +1,13 @@
+{
+  "name": "Holesail Browser",
+  "short_name": "Holesail",
+  "description": "P2P Holesail tunnels in the browser",
+  "start_url": "dashboard.html",
+  "display": "standalone",
+  "background_color": "#0f1117",
+  "theme_color": "#0f1117",
+  "icons": [
+    { "src": "../icons/48.png",  "sizes": "48x48",   "type": "image/png" },
+    { "src": "../icons/128.png", "sizes": "128x128", "type": "image/png" }
+  ]
+}

extension/manifest.json

@@ -53,6 +53,7 @@
         "vendor/novnc.js",
         "wrong-domain.html",
         "dashboard/dashboard.html",
+        "dashboard/manifest.webmanifest",
         "dashboard/dashboard.css",
         "dashboard/data/*.js",
         "dashboard/core/*.js",