Update investigation report with macOS behavior research

Added comprehensive research on macOS default behavior for Issue #4650:

Issue 1 - Window.hide() / Tray Icon UPDATE:
**CRITICAL FINDING**: This is likely macOS default behavior with ActivationPolicyAccessory

Research findings:
- Wails v3 supports NSApplicationActivationPolicy configuration
- Set via options.Mac.ActivationPolicy during ApplicationDidFinishLaunching
- ActivationPolicyAccessory (common for tray apps) can cause status items to hide when all windows are hidden
- This is documented in multiple sources:
  * Wails issues #4103, #3374, #4389
  * Stack Overflow discussions on NSApplicationActivationPolicy
  * GitHub issue #789 (Maccy): Menu bar icon disappears in macOS Sequoia
  * Apple Developer documentation

Root cause analysis:
- Apps using ActivationPolicyAccessory hide from Dock
- macOS may hide status bar items when no windows are visible
- This appears to be intentional macOS behavior, not a bug

Recommended actions updated:
1. Confirm user's activation policy setting
2. Test with ActivationPolicyRegular vs Accessory
3. Suggest workarounds (keep window visible, use Regular policy)
4. Verify if behavior is new in macOS Sequoia 15.5

Added references:
- Application activation policy implementation in v3
- Related Wails issues and online resources
- macOS API documentation
- Community discussions and known issues

Issue 2 remains unchanged - white flicker during maximize is a known
window background color issue.

Issue: wailsapp/wails#4650