Make Applications a real app manager, and clean up storage without the racket

Claude-Session: https://claude.ai/code/session_01Ms2FbjQy31TVf3CEvQhGM8

config/dot/quickshell/services/Snapshots.qml

@@ -44,6 +44,26 @@ Singleton {
     // inside the handler that changes it. See DefaultApps.qml.
     readonly property bool busy: query.running || mutation.running
 
+    // How many snapshots a horizon may keep. The page offers a dropdown rather
+    // than a number field, and this is what fills it; the helper refuses
+    // anything above it too. 999 hourly snapshots is not a retention policy,
+    // it is a typo that fills a drive.
+    //
+    // The monthly and yearly limits are not editable here and are never
+    // written, so a configuration with longer horizons keeps them.
+    readonly property int retentionMax: 50
+    readonly property var retentionChoices: {
+        const values = [];
+        for (let index = 0; index <= root.retentionMax; index += 1)
+            values.push(index);
+        return values;
+    }
+
+    // The card the browser lives in is not the card it was opened from: the
+    // browse state below is independent of any config row's expanded state, so
+    // opening a snapshot from a collapsed row still shows the files.
+    readonly property bool browserOpen: root.browsingConfig !== ""
+
     function labelFor(config: var): string {
         const subvolume = String(config?.subvolume ?? "");
         if (subvolume === "/")
@@ -128,8 +148,21 @@ Singleton {
         root.run(["delete", config, String(number)]);
     }
 
+    // Three horizons, each a whole number the dropdown offered. Checked here as
+    // well as in the helper because the caller is a page that can be wrong, and
+    // a keep count that arrives as "5.5" or "-1" would be written straight into
+    // snapper's config file.
     function setRetention(config: string, hourly: int, daily: int, weekly: int): void {
-        root.run(["set-retention", config, String(hourly), String(daily), String(weekly)]);
+        const values = [hourly, daily, weekly];
+        for (const value of values) {
+            const number = Number(value);
+            if (!Number.isInteger(number) || number < 0 || number > root.retentionMax) {
+                root.lastError = "Keep counts go from 0 to " + root.retentionMax + ".";
+                return;
+            }
+        }
+        root.run(["set-retention", config,
+                  String(values[0]), String(values[1]), String(values[2])]);
     }
 
     function setTimeline(config: string, enabled: bool): void {