CLAUDE: McpServer: hold balanced power profile while MCP is running

Spawns attic/elphel-agent-tools/bin/cpu_profile_hold.py on startup,
which calls power-profiles-daemon HoldProfile('balanced') via DBus.
Released automatically via SIGTERM on JVM shutdown.

Design: KDE AC default is power-saver; this hold raises the profile to
balanced (hardware-driven boost under load) while ImageJ is running,
then releases it so the machine drops back to power-saver on exit.
Co-authored-by: Claude <claude@elphel.com>

src/main/java/com/elphel/imagej/mcp/McpServer.java

@@ -45,6 +45,7 @@ import com.sun.net.httpserver.HttpServer;
 
 public class McpServer {
     private static McpServer INSTANCE;
+    private static Process powerHoldProcess;
 
     private final Eyesis_Correction owner;
     private final int port;
@@ -57,6 +58,7 @@ public class McpServer {
         McpFsAccess.ensureConfigured();
         McpServer instance = new McpServer(owner, port);
         instance.start();
+        startPowerHold();
         if (hasReverseSshTunnel(port)) {
             System.out.println("MCP: reverse SSH tunnel detected for port " + port);
         } else {
@@ -66,6 +68,27 @@ public class McpServer {
         return instance;
     }
 
+    private static void startPowerHold() {
+        java.io.File script = new java.io.File(
+                System.getProperty("user.dir"),
+                "attic/elphel-agent-tools/bin/cpu_profile_hold.py");
+        if (!script.exists()) return;
+        try {
+            powerHoldProcess = new ProcessBuilder("python3", script.getAbsolutePath())
+                    .redirectErrorStream(true)
+                    .start();
+            Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+                if (powerHoldProcess != null && powerHoldProcess.isAlive()) {
+                    powerHoldProcess.destroy();
+                }
+            }, "cpu-profile-hold-release"));
+            System.out.println("MCP: power profile hold started (balanced, pid="
+                    + powerHoldProcess.pid() + ")");
+        } catch (Exception e) {
+            System.out.println("MCP: could not start power profile hold: " + e.getMessage());
+        }
+    }
+
     private static boolean hasReverseSshTunnel(int port) {
         String needle = "127.0.0.1:" + port + ":127.0.0.1:" + port;
         final boolean[] found = new boolean[] { false };