fix: stabilize menu-bar icon on macOS 26

[g150446]

Summary

This PR makes the menu-bar status item more stable on macOS 26 by:

1. Rendering all three glyph states into the same natural-size canvas so the status slot width never changes when toggling between off / on / armed.
2. Using a square-length status item with an explicit autosaveName and isVisible = true.
3. Recreating the status item automatically if its backing button becomes nil.
4. Replacing the layer-based pulse animation with an AppKit animator proxy to avoid touching NSStatusBarButton's layer, which can destabilize status items on newer macOS.

Related

• Closes Icon disappear right after I run the app #2 (in my environment the icon was actually hidden by menu-bar overflow; clearing other items made it reappear. These changes remove other reasons the icon can vanish.)
• Complements / extends Fix menu-bar icon sizing stability #1

Tested

• Built with ./build.sh
• App launches and runs without crashing
• Status item is correctly created with a valid image and button