#69 Fix infinite recursion crash in FileDropOverlayView.mouseDown

Summary

• Fixes 6 crashes (Feb 18) + 4 hangs + 2 CPU resource violations (Feb 17) caused by infinite recursion in FileDropOverlayView.forwardEvent()
• The hide-send-unhide mouse forwarding pattern recurses because NSWindow.sendEvent: routes the event back to the same overlay view without re-doing hit testing
• Adds a simple isForwarding reentrancy guard to break the cycle

Test plan

• Launch app, click around terminal splits — mouse events still pass through the overlay
• Drag files from Finder onto terminal splits — drops still work
• Verify no crashes in Console.app / crash reporter after extended use

🤖 Generated with Claude Code