Add WDA_EXCLUDEFROMCAPTURE support to hide edge light from screen capture

[Copilot]

Implements the Windows WDA_EXCLUDEFROMCAPTURE display affinity flag so the edge light remains visible locally but invisible to screen sharing apps (Teams, Zoom) and screenshot tools. Made optional since screenshots won't capture the effect when enabled.

Changes

Core Implementation

• P/Invoke SetWindowDisplayAffinity with WDA_EXCLUDEFROMCAPTURE (0x00000011)
• Apply to all window types: main overlay, control toolbar, additional monitors
• Store Win32 error codes immediately after API calls for accurate debug logging

Settings Persistence

• JSON configuration in %APPDATA%\WindowsEdgeLight\settings.json
• Automatic recovery from corrupted files with validation

UI Controls

• Control toolbar: 🎥 button with state-aware tooltips
• Tray menu: checkmark toggle for quick access
• Button opacity reflects active state (1.0 enabled, 0.5 disabled)

// Applied during window initialization
SetWindowDisplayAffinity(hwnd, 
    settings.ExcludeFromCapture ? WDA_EXCLUDEFROMCAPTURE : WDA_NONE);

Setting defaults to false to preserve existing screenshot behavior.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Exclude the edge lighting from being captured</issue_title>
<issue_description>use the WDA_EXCLUDEFROMCAPTURE flag so when you are screen sharing, it shouldn't capture.

This should be a setting as well as with this set, you won't be able to take a screenshot with it actually working :)</issue_description>

<agent_instructions>What would this look like? Consider a plan and think about it. If someone shares their screen on teams WHILE using the Edge light, could this flag make it appear invisible to the viewer on the other side?</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Exclude the edge lighting from being captured #20

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