fix(apps): winget bootstrap never ran (unbalanced-brace parse error in inline cmd)

appinstall.log on the VM showed: bootstrap-winget exit=1 'Unexpected token }'. The
inline -Command was built from an interpolated string ($"...{{...}}" -> {/}) concatenated
with a NON-interpolated string whose '}}' stayed literal, so the emitted PowerShell ended
in '}}' and failed to parse -> the bootstrap (and thus winget install) never executed ->
all apps skipped on every run, regardless of network. Invoke the bootstrap .ps1 file
directly instead (it self-checks + installs winget online); fall back to the inbox
re-register only when the script is absent.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

windows/welcome/src/SilverOS.Welcome.Core/Apps/AppInstaller.cs

@@ -79,12 +79,16 @@ public sealed class AppInstaller(IProcessRunner runner, string appsDir) : IAppIn
         Log($"winget probe (PATH): exit={p1.ExitCode} out={Snip(p1.StdOut)}");
         if (p1.ExitCode == 0) return "winget";
 
-        // 2) Provision App Installer via the bundled bootstrap (or registered package), then re-probe.
+        // 2) Provision App Installer, then re-probe. Run the bootstrap SCRIPT FILE directly
+        //    (it checks for winget and installs it online if absent). Invoking the .ps1 file
+        //    avoids an inline -Command (a prior inline if/else had an unbalanced-brace parse bug
+        //    from a non-interpolated string, so the bootstrap never actually ran).
         progress.Report(new("Preparing app installer", 68));
         var bootstrap = Path.Combine(appsDir, "bootstrap-winget.ps1");
-        var b = await TryRunAsync("powershell.exe",
-            $"-NoProfile -ExecutionPolicy Bypass -Command \"if (Test-Path '{bootstrap}') {{ & '{bootstrap}' }} else {{ " +
-            "Add-AppxPackage -RegisterByFamilyName -MainPackage Microsoft.DesktopAppInstaller_8wekyb3d8bbwe -EA SilentlyContinue }}\"",
+        var b = File.Exists(bootstrap)
+            ? await TryRunAsync("powershell.exe", $"-NoProfile -ExecutionPolicy Bypass -File \"{bootstrap}\"", ct)
+            : await TryRunAsync("powershell.exe",
+                "-NoProfile -ExecutionPolicy Bypass -Command \"Add-AppxPackage -RegisterByFamilyName -MainPackage Microsoft.DesktopAppInstaller_8wekyb3d8bbwe -EA SilentlyContinue\"",
                 ct);
         Log($"bootstrap-winget: exit={b.ExitCode} out={Snip(b.StdOut)} err={Snip(b.StdErr)}");
         var p2 = await TryRunAsync("winget", "--version", ct);