How the pill behaves, and why

Levels, clicks, hover timing, other notch apps and menu bar managers.

Overview

What	How	Why
Window level	27 (`.mainMenu + 3`) when the notch is ours, 25 while sharing it, 100 while hovered	neighbors open over us; clicks reach us; pop-up menus (101) stay on top
Clicks	only while hovered, only over the pill as drawn	a transparent window that takes mouse events takes them over its whole frame
Hover	opens after 140 ms, closes 350 ms after leaving	passing over the notch on the way to a menu doesn't pop it open
Option-hover	hands a shared notch to the other app until the pointer leaves	so the other app's panel can be used
Status dot pulse	Core Animation, played by the window server	a SwiftUI `repeatForever` cost about 9% CPU

Known apps are matched by bundle ID prefix; unknown ones by a window hanging from the top edge over the notch, seen twice 0.3 s apart, then remembered until that app quits. com.apple.*, full-width strips, popovers and full-screen overlays never count.
With one there, the pill hangs just below the notch (setting: sharing). A menu bar manager's bar of hidden items (Bartender, Ice, Thaw…) pushes it under the bar while open.
The window list is read twice a second only while something of ours shows near the notch; otherwise every 10 s.
Agent apps (most notch apps) don't post launch and quit notifications, so the monitor watches the running applications list instead.

On macOS 27 the menu bar is one window, so the free space beside the notch can't be measured without extra permissions. That's why "Keep the menu bar clear" (pillShape) and the indicator position are settings.
The package never moves or hides other apps' menu bar items and asks for no Accessibility or Screen Recording permission.