Fix macOS interactive feedback visibility and add native dialog fallback

[LelandJin]

Summary

This PR improves the reliability of interactive-feedback-mcp on macOS.

The previous behavior could fail in two ways:

• the feedback window could open off-screen or fail to come to the foreground
• the MCP flow could still fail even when the UI path was not reliable

To address this, this change:

• adds macOS window management helpers to bring the PySide window to the front
• ensures restored windows are still visible on an active screen
• centers the window on the primary screen when needed
• adds a native macOS dialog fallback in server.py for feedback collection
• wraps MCP stdio startup more safely to avoid noisy interruption behavior

Changes

• Added macOS-specific window activation logic in feedback_ui.py
• Added window centering and on-screen visibility checks in feedback_ui.py
• Improved initial window focus behavior when the UI is shown
• Added a native AppleScript-based feedback dialog fallback in server.py for macOS
• Kept the existing stdio MCP flow intact while improving reliability on macOS

Why

The goal is to make interactive feedback consistently usable on macOS, especially when:

• the saved window position is invalid
• the feedback UI is launched behind other windows
• the PySide UI path is less reliable than a native system dialog

Validation

• Verified Python syntax with py_compile
• Verified the native macOS dialog path can return user input successfully
• Verified interactive-feedback-mcp can receive feedback through the intended tool path

Impact

This change is scoped to the interactive-feedback-mcp project and primarily affects macOS behavior.
Non-macOS platforms continue to use the existing feedback UI flow.