Tests: opt-in real Windows-service lifecycle (install/start/stop/uninstall)

Local checkpoint - NOT for public release.

New self-test "Service real lifecycle" drives the ACTUAL SCM end to end: install ->
report installed -> start -> report running -> stop -> report stopped -> uninstall ->
report gone. Needs admin, so it's OPT-IN via REMSOUND_TEST_SERVICE=1 and skips cleanly
in the normal unprivileged gate. It clears any leftover registration first (DoUninstall
stops a running copy, so a stray from an aborted run can't fail it) and always removes
the service afterwards, even on failure - so it never leaves a service pointing at a
throwaway exe. Run elevated: set REMSOUND_TEST_SERVICE=1 then RemSound.exe --selftest.

The app-yield takeover is already covered headlessly by "Service send host (stream +
yield)"; a full real end-to-end (installed service goes quiet when the app opens) needs
a live peer to observe and stays a manual check. Gate 26 passed, 1 skipped of 27.

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

src/RemSound.App/SelfTest.cs

@@ -66,6 +66,7 @@ internal static class SelfTest
         RunStep(results, "Service sender parity (crypto + Opus frame)", ServiceSenderParity);
         RunStep(results, "Service send host (headless stream + yield)", ServiceSendHostStream);
         RunStep(results, "Service registration args", ServiceRegistrationArgs);
+        RunStep(results, "Service real lifecycle (install/start/stop/uninstall)", ServiceRealLifecycle);
         RunStep(results, "Recording engine (all formats + source gate + mono)", RecordingEngine);
         RunStep(results, "Recording split tracks (per-peer + own)", RecordingSplitTracks);
         RunStep(results, "Recording churn / soak", RecordingChurn);
@@ -661,6 +662,59 @@ internal static class SelfTest
         return File.Exists(path) ? new FileInfo(path).Length : 0;
     }
 
+    /// <summary>The REAL Windows-service lifecycle end to end: install → started → stopped → uninstalled,
+    /// driving the actual SCM (sc.exe + ServiceController). Needs administrator rights, so it's OPT-IN via
+    /// REMSOUND_TEST_SERVICE=1 and skips cleanly otherwise — the normal gate runs unprivileged. It clears
+    /// any leftover registration first (so a stray copy from an aborted run can't fail it) and always
+    /// removes the service afterwards, even on failure. Run it elevated:
+    ///   set REMSOUND_TEST_SERVICE=1 &amp;&amp; RemSound.exe --selftest   (from an elevated prompt)</summary>
+    private static string? ServiceRealLifecycle()
+    {
+        if (!string.Equals(Environment.GetEnvironmentVariable("REMSOUND_TEST_SERVICE"), "1", StringComparison.Ordinal))
+            return Skip("set REMSOUND_TEST_SERVICE=1 (elevated) to run the real install/start/stop/uninstall lifecycle");
+        if (!IsAdministrator())
+            return Skip("the real service lifecycle needs administrator rights");
+
+        // Start from a known state — remove any service left over from a previous aborted run. DoUninstall
+        // stops it first, so this also clears a leftover RUNNING copy.
+        if (ServiceControl.IsInstalled()) ServiceControl.DoUninstall();
+        Check(!ServiceControl.IsInstalled(), "pre-clean: no leftover RemSound service should remain");
+
+        try
+        {
+            Check(ServiceControl.DoInstall() == 0, "DoInstall should succeed");
+            Check(ServiceControl.IsInstalled(), "the service should report installed after DoInstall");
+            Check(ServiceControl.Query() == ServiceState.Stopped, "an auto-start service is Stopped until started");
+
+            Check(ServiceControl.DoStart() == 0, "DoStart should succeed");
+            Check(ServiceControl.Query() == ServiceState.Running, "the service should be Running after DoStart");
+
+            Check(ServiceControl.DoStop() == 0, "DoStop should succeed");
+            Check(ServiceControl.Query() == ServiceState.Stopped, "the service should be Stopped after DoStop");
+
+            Check(ServiceControl.DoUninstall() == 0, "DoUninstall should succeed");
+            Check(!ServiceControl.IsInstalled(), "the service should be gone after DoUninstall");
+
+            return "installed → started → stopped → uninstalled (real SCM)";
+        }
+        finally
+        {
+            // Safety net: never leave a service registered (its binPath would point at a throwaway exe).
+            try { if (ServiceControl.IsInstalled()) ServiceControl.DoUninstall(); } catch { /* best-effort */ }
+        }
+    }
+
+    private static bool IsAdministrator()
+    {
+        try
+        {
+            using var id = System.Security.Principal.WindowsIdentity.GetCurrent();
+            return new System.Security.Principal.WindowsPrincipal(id)
+                .IsInRole(System.Security.Principal.WindowsBuiltInRole.Administrator);
+        }
+        catch { return false; }
+    }
+
     /// <summary>The sc.exe "create" argument string quotes a spaced exe path correctly — a real footgun
     /// (a broken binPath silently installs a service that can't start). Pure/side-effect-free, so it
     /// never touches the SCM or needs admin.</summary>