Service: remove the confusing Update-service menu item; make bin folder user-writable

Ed: a menu item a user has to know when to click is the wrong answer -- real users get
the service via the automatic self-update (version bump), full stop. Remove the menu item.

For developer/tester same-version refreshes, honour "stop it and update it": install now
grants Authenticated Users Modify on the service bin folder (icacls), so once the service
is stopped its binaries can be replaced with no admin -- the exact workflow Ed asked for.
Same trust posture as the auto-update copy (user-writable content run as SYSTEM); noted
for a future code-signed hardening.

The --update-service verb / DoUpdate stay as internal plumbing (no user-facing entry).

Gate: 40/40.

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

src/RemSound.App/MainForm.cs

@@ -2228,8 +2228,6 @@ public sealed class MainForm : Form
         install.Click += (_, _) => ServiceAction(ServiceControl.InstallVerb, "install", confirm: true);
         var uninstall = new ToolStripMenuItem("&Uninstall service") { AccessibleName = "Uninstall service" };
         uninstall.Click += (_, _) => ServiceAction(ServiceControl.UninstallVerb, "uninstall", confirm: true);
-        var update = new ToolStripMenuItem("Up&date service to this version") { AccessibleName = "Update service to this version — copies the currently-running RemSound build into the service" };
-        update.Click += (_, _) => ServiceAction(ServiceControl.UpdateVerb, "update", confirm: false);
         var start = new ToolStripMenuItem("S&tart service") { AccessibleName = "Start service" };
         start.Click += (_, _) => ServiceAction(ServiceControl.StartVerb, "start", confirm: false);
         var stop = new ToolStripMenuItem("Sto&p service") { AccessibleName = "Stop service" };
@@ -2243,7 +2241,7 @@ public sealed class MainForm : Form
         {
             status, new ToolStripSeparator(),
             configure, new ToolStripSeparator(),
-            install, uninstall, update, start, stop, new ToolStripSeparator(),
+            install, uninstall, start, stop, new ToolStripSeparator(),
             activityLog, updateLog,
         });
         serviceMenu.DropDownOpening += (_, _) =>
@@ -2263,7 +2261,6 @@ public sealed class MainForm : Form
                 var installed = state != ServiceState.NotInstalled;
                 install.Enabled = !installed;
                 uninstall.Enabled = installed;
-                update.Enabled = installed; // refresh the service's copy with the running build (stop→copy→start)
                 start.Enabled = installed && state is ServiceState.Stopped;
                 stop.Enabled = installed && state is ServiceState.Running;
             }

src/RemSound.App/ServiceControl.cs

@@ -120,9 +120,38 @@ public static class ServiceControl
         RunSc(BuildFailureArgs());
         // Let a normal (non-admin) user start/stop it — otherwise stopping needs the app's UAC prompt.
         GrantUserStartStop();
+        // Let a normal user REPLACE the binaries in the service's bin folder too (once the service is
+        // stopped), so a new build can be dropped in without admin — the auto-updater does this as SYSTEM,
+        // but it also makes "stop the service, copy the new files in, start it" work for a developer/tester
+        // with no UAC. (Trust note: a user-writable folder whose contents run as SYSTEM is the same posture
+        // as the auto-update copy; fine for this app, a hardened build would code-sign instead.)
+        GrantUsersWriteToBin();
         return 0;
     }
 
+    /// <summary>Grant Authenticated Users Modify rights on the service's bin folder (via icacls), so a
+    /// stopped service's binaries can be refreshed without administrator rights. Best-effort.</summary>
+    private static void GrantUsersWriteToBin()
+    {
+        try
+        {
+            // *S-1-5-11 = Authenticated Users (locale-independent). (OI)(CI) = inherit to files+subfolders; M = Modify.
+            var psi = new ProcessStartInfo
+            {
+                FileName = "icacls.exe",
+                Arguments = $"\"{ServiceStore.BinDirectory}\" /grant \"*S-1-5-11:(OI)(CI)M\" /T /C /Q",
+                UseShellExecute = false,
+                CreateNoWindow = true,
+                RedirectStandardOutput = true,
+                RedirectStandardError = true,
+            };
+            using var p = Process.Start(psi);
+            p?.WaitForExit(20000);
+            if (p is { ExitCode: not 0 }) ServiceStore.AppendServiceEvent($"install: icacls grant-write on bin returned {p.ExitCode}");
+        }
+        catch (Exception ex) { ServiceStore.AppendServiceEvent($"install: grant-write on bin failed: {ex.GetType().Name}: {ex.Message}"); }
+    }
+
     /// <summary>Copies the program files from <paramref name="sourceDir"/> to <paramref name="destDir"/>,
     /// recursively, but NEVER the user-state folders (logs, profiles, config, recordings) — the service
     /// keeps its own state in ProgramData. Overwrites so a re-install refreshes the binaries.</summary>