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/modules/app_name_toast.lua

@@ -0,0 +1,58 @@
+local AppNameToast = {}
+AppNameToast.__index = AppNameToast
+
+function AppNameToast.new(config)
+  return setmetatable({
+    config = config,
+    alertId = nil,
+    commandKeyDown = false,
+    commandKeyWatcher = nil,
+    shouldShow = nil,
+  }, AppNameToast)
+end
+
+function AppNameToast:setShouldShow(predicate)
+  self.shouldShow = predicate
+end
+
+function AppNameToast:show()
+  if not self.config.enabled then return end
+  if self.shouldShow and not self.shouldShow() then return end
+
+  local win = hs.window.focusedWindow()
+  local app = win and win:application() or nil
+  if not app then return end
+
+  if self.alertId then
+    hs.alert.closeSpecific(self.alertId, 0)
+  end
+
+  self.alertId = hs.alert.show(
+    app:name(),
+    self.config.style,
+    win:screen(),
+    self.config.duration
+  )
+end
+
+function AppNameToast:start()
+  if not self.config.showOnCommand then return self end
+
+  self.commandKeyWatcher = hs.eventtap.new({
+    hs.eventtap.event.types.flagsChanged,
+  }, function(event)
+    local isCommandDown = event:getFlags().cmd == true
+
+    if isCommandDown and not self.commandKeyDown then
+      self:show()
+    end
+
+    self.commandKeyDown = isCommandDown
+    return false
+  end)
+  self.commandKeyWatcher:start()
+
+  return self
+end
+
+return AppNameToast