feat(hammerspoon): show app name on focus and command key

Extract window highlighting into a dedicated module and centralize shared
configuration. Add a configurable app name toast triggered by focus changes
and Command key presses.

hammerspoon/.hammerspoon/config.lua

@@ -0,0 +1,41 @@
+local accentColor = {
+  red = 0.25,
+  green = 0.65,
+  blue = 1.0,
+  alpha = 0.95,
+}
+
+return {
+  windowHighlight = {
+    borderWidth = 5,
+    padding = 4,
+    radius = 10,
+    color = accentColor,
+
+    animation = true,
+    animationDuration = 0.10,
+    animationSteps = 8,
+
+    hideOnFullscreen = false,
+    framePollingFps = 30,
+  },
+
+  appNameToast = {
+    enabled = true,
+    duration = 0.7,
+    showOnFocus = true,
+    showOnCommand = true,
+
+    style = {
+      fillColor = { white = 0.08, alpha = 0.88 },
+      strokeColor = accentColor,
+      strokeWidth = 2,
+      textColor = { white = 1, alpha = 1 },
+      textSize = 20,
+      padding = 10,
+      radius = 10,
+      fadeInDuration = 0.08,
+      fadeOutDuration = 0.12,
+    },
+  },
+}