terra: migrate quickshell config into repo, add quickshell + opencode packages

Config was symlinked from ~/.dots/quickshell (separate dotfiles repo); now
tracked here and applied via home-manager xdg.configFile.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

dotfiles/quickshell/widgets/launcher/LauncherState.qml

@@ -0,0 +1,14 @@
+pragma Singleton
+
+import Quickshell
+import QtQuick
+
+// Shared launcher state so other widgets (e.g. the top bar) can react to the
+// launcher without a direct dependency on it.
+Singleton {
+    // True while the "Console" launcher (variant 4) is open — top bar reacts.
+    property bool consoleOpen: false
+
+    // True while the "Dock" launcher (variant 5) is open — bottom bar reacts.
+    property bool dockOpen: false
+}