Treat idle timeout 0 as disabled, not immediate

idle.screensaver / idle.lock of 0 was included in Math.min(), so
IdleMonitor's timeout became 0. Releasing a Wayland idle inhibitor
(SDL's default screensaver inhibit) then reported idle immediately and
locked the session even when lock had been "disabled" by setting it to 0.

Treat 0 as disabled when computing the first idle deadline, do not start
the corresponding action, and leave IdleMonitor off when both timeouts
are 0.

Fixes #10860

shell/plugins/services/idle/Service.qml

@@ -20,9 +20,12 @@ Item {
     ? shell.shellConfig.idle : (shell && shell.idleConfig ? shell.idleConfig : ({}))
   readonly property int screensaverTimeoutSeconds: secondsFromConfig(idleConfig.screensaver, defaultScreensaverSeconds)
   readonly property int lockTimeoutSeconds: secondsFromConfig(idleConfig.lock, defaultLockSeconds)
-  readonly property int firstIdleTimeoutSeconds: Math.min(screensaverTimeoutSeconds, lockTimeoutSeconds)
-  readonly property int screensaverDelaySeconds: Math.max(0, screensaverTimeoutSeconds - firstIdleTimeoutSeconds)
-  readonly property int lockDelaySeconds: Math.max(0, lockTimeoutSeconds - firstIdleTimeoutSeconds)
+  readonly property bool screensaverEnabled: screensaverTimeoutSeconds > 0
+  readonly property bool lockEnabled: lockTimeoutSeconds > 0
+  readonly property bool idleTimersEnabled: screensaverEnabled || lockEnabled
+  readonly property int firstIdleTimeoutSeconds: IdleModel.firstIdleTimeout(screensaverTimeoutSeconds, lockTimeoutSeconds)
+  readonly property int screensaverDelaySeconds: IdleModel.delayAfterFirstIdle(screensaverTimeoutSeconds, firstIdleTimeoutSeconds)
+  readonly property int lockDelaySeconds: IdleModel.delayAfterFirstIdle(lockTimeoutSeconds, firstIdleTimeoutSeconds)
   readonly property bool idleEnabled: stayAwakeStateLoaded && !stayAwake
   readonly property string screensaverClass: "org.omarchy.screensaver"
 
@@ -91,11 +94,15 @@ Item {
     root.screensaverStartedThisCycle = false
     resetScreensaverWindows()
 
-    if (root.screensaverDelaySeconds === 0) launchScreensaver()
-    else screensaverTimer.restart()
+    if (root.screensaverEnabled) {
+      if (root.screensaverDelaySeconds === 0) launchScreensaver()
+      else screensaverTimer.restart()
+    }
 
-    if (root.lockDelaySeconds === 0) lockSystem("lock-timeout-immediate")
-    else lockTimer.restart()
+    if (root.lockEnabled) {
+      if (root.lockDelaySeconds === 0) lockSystem("lock-timeout-immediate")
+      else lockTimer.restart()
+    }
   }
 
   function cancelIdleCycle(reason) {
@@ -172,7 +179,7 @@ Item {
 
   function handleIdleChanged() {
     logEvent("idle-monitor", idleMonitor.isIdle ? "idle" : "active")
-    if (!root.idleEnabled) return
+    if (!root.idleEnabled || !root.idleTimersEnabled) return
 
     if (idleMonitor.isIdle) startIdleCycle()
     else handleActiveSignal()
@@ -250,8 +257,8 @@ Item {
 
   IdleMonitor {
     id: idleMonitor
-    enabled: root.idleEnabled
-    timeout: root.firstIdleTimeoutSeconds
+    enabled: root.idleEnabled && root.idleTimersEnabled
+    timeout: Math.max(1, root.firstIdleTimeoutSeconds)
     respectInhibitors: true
     onIsIdleChanged: root.handleIdleChanged()
   }