Feature: Add signature status column to commit table

[MatriQ]

Feature Description

Add a new column to the main commit list view in Git Graph to display the commit signature status.

Use Case

When working with signed commits in a repository, it's important to quickly identify which commits have valid signatures, which have invalid signatures, and which are unsigned. Currently, signature information is only shown in the Commit Details View when showSignatureStatus is enabled. Having a dedicated column in the main table would provide at-a-glance verification of commit authenticity.

Proposed Implementation

• Add a new Signature column to defaultColumnVisibility configuration (enabled by default)
• Modify git log format to include signature data (%G?, %GS, %GK)
• Display signature status using icons with color coding:
  • ✓ Green (G) - Good signature
  • ✗ Red (B, R) - Bad or Revoked signature
  • ⚠ Orange (U, X, Y) - Warning states
  • ❓ Gray (E) - Cannot check
  • - Gray - No signature
• Hover tooltip shows detailed info (signer, key ID)

Benefits

• Quick visual verification of commit authenticity
• Consistent with the existing signature display in Commit Details View
• Helps maintain security awareness in collaborative projects

Additional Notes

The extension already has signature support in the Commit Details View. This feature would extend that capability to the main table view for better visibility.