fix: critical XAML binding bug + clean up temp file lifecycle

User looked at %TEMP% and asked what was there. Found three real
issues, all fixed.

1. CRITICAL: ApplyResultsWindow XAML had Run.Text="{Binding Before}"
   etc. on read-only properties of ResultRow. WPF's default Run.Text
   binding is TwoWay, which fails on get-only properties with the
   error "A TwoWay or OneWayToSource binding cannot work on the
   read-only property 'Before'." Confirmed in user's
   %TEMP%\gamerguardian_error.log — they triggered Apply in v0.1.18,
   the window threw during measure, and they never saw the
   verification details. Added Mode=OneWay to all four Run bindings
   (Before, Desired, After, Mechanism). Will be fixed for users on
   v0.1.20+.

2. Stale installer EXEs from the auto-update flow (~75 MB each)
   were piling up in %TEMP%. UpdateService.DownloadInstallerAsync
   writes them, launches them, then exits — never cleans up.
   New TempCleanup.Run() called from OnStartup deletes any
   GamerGuardian-Setup-*.exe in %TEMP% older than 1 day (1-day
   grace so an in-progress install isn't yanked). Also one-shot
   removes any stale gamerguardian_trace.log file from earlier dev
   builds.

3. gamerguardian_error.log was append-only with no cap. Now rotates
   at ~1 MB (.log -> .log.1) the same way changes.log does.

README gains a "Files GamerGuardian writes" table that documents
every path the app touches: install location, config, change log,
error log, self-test output, downloaded installers, autostart key.
Includes the "auto-cleaned on next launch" note for stale installer
downloads so users on v0.1.20+ know they don't need to manually
delete them.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: carterscode

README.md

@@ -225,7 +225,9 @@ GamerGuardian doesn't ask you to take its word for it.
 | Power plan | `powercfg /getactivescheme` |
 | HDR / Refresh / Resolution | Settings → System → Display, or `dxdiag` |
 
-**4. The change log.** `%APPDATA%\GamerGuardian\changes.log` — every applied change (manual or silent auto-apply) is appended with a timestamp, source, before/after values, and verification status. Open it from *Settings → General → Open change log*, or from the Apply Results window. Sample line:
+**4. The change log.** `%APPDATA%\GamerGuardian\changes.log` — every applied change (manual or silent auto-apply) is appended with a timestamp, source, before/after values, and verification status. Open it from *Settings → General → Open change log*, or from the Apply Results window. Auto-rotates at ~1 MB.
+
+Sample line:
 
 ```
 [2026-05-06 22:14:08] [manual] OK     USB Selective Suspend (global override)  |  Default -> Disabled (gaming)  |  now: Disabled (gaming) | reboot pending
@@ -237,6 +239,20 @@ Auto-rotates at ~1 MB (`changes.log.1` keeps the previous batch).
 
 **6. The source.** Every monitor is a single file under [`src/GamerGuardian/Monitors/`](src/GamerGuardian/Monitors/) that does exactly one thing each. Read [`HagsMonitor.cs`](src/GamerGuardian/Monitors/HagsMonitor.cs), say, to see the full code that reads and writes HAGS — about 30 lines.
 
+## Files GamerGuardian writes
+
+| Path | Purpose | Lifetime |
+|---|---|---|
+| `%LOCALAPPDATA%\Programs\GamerGuardian\GamerGuardian.exe` | Installed app | Until uninstall |
+| `%APPDATA%\GamerGuardian\config.json` | Your monitor / want / auto-apply preferences | Persists; survives upgrades |
+| `%APPDATA%\GamerGuardian\changes.log` | Append-only audit of every applied change | Auto-rotates at ~1 MB → `changes.log.1` |
+| `%TEMP%\gamerguardian_error.log` | Unhandled-exception stack traces (rare) | Auto-rotates at ~1 MB → `.log.1` |
+| `%TEMP%\gamerguardian_selftest.txt` | Output of `GamerGuardian.exe --test` | Overwritten each run |
+| `%TEMP%\GamerGuardian-Setup-x.y.z.exe` | Installer downloaded by the auto-update flow before it launches | **Auto-cleaned on next launch** if older than 1 day |
+| `HKCU\Software\Microsoft\Windows\CurrentVersion\Run\GamerGuardian` | Launch-at-startup entry | Created/removed by the *Launch at Windows startup* checkbox |
+
+If you see leftover `GamerGuardian-Setup-*.exe` files in `%TEMP%` from before v0.1.20, you can delete them — they were the previous auto-update flow's downloaded installers. v0.1.20+ cleans them up automatically.
+
 ## Compatibility
 
 - **Windows 11** (any version). Windows 10 support is on the roadmap.

src/GamerGuardian/App.xaml.cs

@@ -49,6 +49,7 @@ protected override void OnStartup(StartupEventArgs e)
         var cfg = _store.Load();
         StartupRegistration.Sync(cfg.LaunchAtStartup);
         ThemeService.Apply(cfg.Theme);
+        TempCleanup.Run();
 
         _notifier = new Notifier();
         _allMonitors = new IMonitoredSetting[]
@@ -180,6 +181,18 @@ private static void LogException(string source, Exception? ex)
         try
         {
             var path = System.IO.Path.Combine(System.IO.Path.GetTempPath(), "gamerguardian_error.log");
+            // Cap at ~1 MB by rotating to .1
+            try
+            {
+                var fi = new System.IO.FileInfo(path);
+                if (fi.Exists && fi.Length > 1_000_000)
+                {
+                    var prev = path + ".1";
+                    if (System.IO.File.Exists(prev)) System.IO.File.Delete(prev);
+                    System.IO.File.Move(path, prev);
+                }
+            }
+            catch { }
             System.IO.File.AppendAllText(path,
                 $"[{DateTime.Now:s}] {source}: {ex?.GetType().FullName}: {ex?.Message}\n{ex?.StackTrace}\n\n");
         }

src/GamerGuardian/Services/TempCleanup.cs

@@ -0,0 +1,44 @@
+using System.IO;
+
+namespace GamerGuardian.Services;
+
+/// <summary>
+/// Best-effort cleanup of stale GamerGuardian artifacts in %TEMP%:
+///  - Old installer EXEs left behind by the auto-update flow.
+///  - Old trace.log files from earlier dev builds.
+/// Files newer than 1 day are kept so an in-progress install isn't disturbed.
+/// </summary>
+public static class TempCleanup
+{
+    private const int KeepDays = 1;
+
+    public static void Run()
+    {
+        try
+        {
+            var temp = Path.GetTempPath();
+            var cutoff = DateTime.Now.AddDays(-KeepDays);
+
+            foreach (var path in Directory.EnumerateFiles(temp, "GamerGuardian-Setup-*.exe"))
+            {
+                TryDeleteIfOlder(path, cutoff);
+            }
+
+            var stale = Path.Combine(temp, "gamerguardian_trace.log");
+            TryDeleteIfOlder(stale, DateTime.MaxValue); // always remove — code no longer writes it
+        }
+        catch { /* best-effort */ }
+    }
+
+    private static void TryDeleteIfOlder(string path, DateTime cutoff)
+    {
+        try
+        {
+            var fi = new FileInfo(path);
+            if (!fi.Exists) return;
+            if (fi.LastWriteTime > cutoff) return;
+            fi.Delete();
+        }
+        catch { }
+    }
+}

src/GamerGuardian/UI/ApplyResultsWindow.xaml

@@ -69,16 +69,16 @@
                                         </Border>
                                     </Grid>
                                     <TextBlock Margin="30,4,0,0" FontSize="12">
-                                        <Run Text="Before: "/><Run Text="{Binding Before}" Foreground="{DynamicResource TextFillColorSecondaryBrush}"/>
+                                        <Run Text="Before: "/><Run Text="{Binding Before, Mode=OneWay}" Foreground="{DynamicResource TextFillColorSecondaryBrush}"/>
                                         <Run Text="    →    "/>
-                                        <Run Text="Want: "/><Run Text="{Binding Desired}" Foreground="{DynamicResource TextFillColorSecondaryBrush}"/>
+                                        <Run Text="Want: "/><Run Text="{Binding Desired, Mode=OneWay}" Foreground="{DynamicResource TextFillColorSecondaryBrush}"/>
                                         <Run Text="    →    "/>
-                                        <Run Text="Now: "/><Run Text="{Binding After}" Foreground="{Binding IconColor}" FontWeight="SemiBold"/>
+                                        <Run Text="Now: "/><Run Text="{Binding After, Mode=OneWay}" Foreground="{Binding IconColor}" FontWeight="SemiBold"/>
                                     </TextBlock>
                                     <TextBlock Margin="30,6,0,0" FontSize="11"
                                                Foreground="{DynamicResource TextFillColorTertiaryBrush}"
                                                TextWrapping="Wrap">
-                                        <Run Text="Mechanism: "/><Run Text="{Binding Mechanism}"/>
+                                        <Run Text="Mechanism: "/><Run Text="{Binding Mechanism, Mode=OneWay}"/>
                                     </TextBlock>
                                     <Grid Margin="30,4,0,0" Visibility="{Binding HasVerifyCommandVisibility}">
                                         <Grid.ColumnDefinitions>