gui: Fix keyboard shortcuts for closing windows

[russellhancox]

For notification windows, the existing Cmd+Esc doesn't work and I couldn't find a way to reliably make it work. Switch to Cmd+W instead.

For the More Info pane, switch from Cmd+Esc to just plain Esc.

Also fix the passing of EventDetailURL in SNTTestGUI.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR updates keyboard shortcuts for dismiss buttons across message window views, standardizing to cancelAction/Esc patterns or Cmd+W, and adds URL fallback logic in the Binary display test harness to prefer eventDetailURL when customURL is absent.

Changes

Dismiss Keyboard Shortcuts and URL Fallback

Layer / File(s)	Summary
DismissButton Core Shortcut Source/gui/SNTMessageView.swift	DismissButton updates keyboard shortcut from Cmd+Esc ("⌘ Esc") to Cmd+W ("⌘ W").
MoreDetailsView Dismiss Buttons Source/gui/SNTBinaryMessageWindowView.swift, Source/gui/SNTFileAccessMessageWindowView.swift, Source/gui/SNTNetworkMountMessageWindowView.swift	Dismiss button shortcuts in MoreDetailsView across all three message window types are standardized from Cmd+Esc to .cancelAction with "Esc" help text.
Test Harness URL Fallback Source/gui/SNTTestGUI.swift	Binary display harness computes effectiveURL that falls back to eventDetailURL when customURL is empty, then passes effectiveURL to the factory.

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change—fixing keyboard shortcuts for closing windows—which is the primary purpose of all modifications across the four affected files.
Description check	✅ Passed	The PR description accurately and specifically describes the keyboard shortcut changes across multiple files and the EventDetailURL fix, aligning with the actual changeset.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch rah/gui-fix-cmd-esc

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