[Feature]: macOS Input Monitoring permission flow (global keyboard/mouse)

[theonlyhennygod]

Summary

Add native Input Monitoring (TCC kTCCServiceListenEvent) check/request to the desktop app so global keyboard and pointer events can be observed outside our own windows.

Problem

Without Input Monitoring, the desktop agent cannot:

• Receive global hotkeys when not focused ([Feature]: Global keyboard shortcut to summon/dismiss the menu-bar chat panel #6328 depends on this).
• Observe user activity for context-aware prompting.
• Hook keystroke watchers for dictation alongside the menu-bar chat.

This is a sibling of #6333 (AX), #6334 (Screen Recording), #6335 (Microphone) and is currently the only "core control" permission with no native check or request path.

Proposal

• Add IOKit FFI block in apps/tauri/src/macos/permissions.rs:
  • IOHIDCheckAccess(requestType: u32) -> u32
  • IOHIDRequestAccess(requestType: u32) -> bool
  • Constants: kIOHIDRequestTypeListenEvent = 1, kIOHIDAccessTypeGranted = 0, kIOHIDAccessTypeDenied = 1, kIOHIDAccessTypeUnknown = 2.
• check_input_monitoring() and request_input_monitoring() returning granted / denied / not_determined.
• Extend open_system_settings() with input_monitoring → Privacy_ListenEvent.
• Surface in onboarding wizard alongside AX / Screen Recording.
• Add NSInputMonitoringUsageDescription to Info.plist.

Acceptance

• Native check returns correct status without prompting.
• Native request triggers the macOS Input Monitoring dialog on first call.
• Onboarding wizard shows the permission and reflects the current status.
• Deep-link to System Settings → Privacy & Security → Input Monitoring works.

Related

Implemented as part of feat/desktop-onboarding PR (linked when opened).