StemRoller: desktop stem separator, Android stems player, and server daemons

- stemroller/: PySide6/QML desktop app and player for separating music into stems
- android/: Plex music player that plays per-stem mixes, with Android Auto support,
  a graphic + parametric (Equalizer APO-style) EQ, and offline downloads
- server/: stemserve (serves stems to the app) and stemd (separates the library on
  the server's GPU, with "Stem Now" priority requests)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

stemroller/player/qml/StemPlayer/Tip.qml

@@ -0,0 +1,22 @@
+import QtQuick
+import QtQuick.Controls.Basic
+
+// Office-style tooltip: white box, gray border, after a short hover.
+ToolTip {
+    id: tt
+    property var target
+    visible: target && target.containsMouse && text !== "" && hoverTimer.done
+    delay: 0
+    timeout: 6000
+    padding: 6
+    Timer {
+        id: hoverTimer
+        property bool done: false
+        interval: 600
+        running: tt.target && tt.target.containsMouse
+        onRunningChanged: if (!running) done = false
+        onTriggered: done = true
+    }
+    contentItem: T { text: tt.text; font.pixelSize: X.fsSmall; elide: Text.ElideNone }
+    background: Rectangle { color: "#FFFFFF"; border.color: "#BEBEBE" }
+}