fix: reduce potential menu bar memory growth from oversized collapsed widths

[phucledien]

Summary

This PR addresses high-memory reports (see #326) by removing oversized status item collapse widths that can trigger expensive menu bar layout behavior on newer macOS versions.

Closes #343.

Root cause hypothesis

StatusBarController used very large hardcoded collapse lengths (10000) for status items when hiding sections.
On newer macOS builds, oversized status item geometry appears to cause pathological layout/repaint work, which aligns with reports of Hidden consuming multiple GB of RAM.

What changed

• Replaced hardcoded large collapse lengths with a dynamic bounded width based on current screen width.
  • New bounded formula: max(500, min(screenWidth + 200, 4000))
• Recompute collapse lengths when display configuration changes via:
  • NSApplication.didChangeScreenParametersNotification
• Added cleanup safety:
  • deinit now removes observers.
• Fixed status item lifecycle in always-hidden toggle:
  • Explicitly remove old NSStatusItem from NSStatusBar before replacing/nilling.

Why this is safe

• Behavior remains functionally the same (collapsed section still fully hidden).
• Uses realistic, bounded geometry instead of extreme values.
• Should reduce risk of memory growth while preserving UX.

Validation notes

I couldn’t run full xcodebuild in this environment because full Xcode isn’t installed (only Command Line Tools). Please validate on macOS 15/26 with Activity Monitor after repeated collapse/expand + auto-hide cycles.