Drag visible rulers together when grouped

[pascalpp]

Summary

• Restores the Group Rulers option as synchronized dragging for all visible rulers.
• Preserves each visible ruler's relative position while one grouped ruler is dragged.
• Reorders and renames the related Options menu commands for grouping, mouse alignment, and reset position.

Tests

• xcodebuild -project "Free Ruler.xcodeproj" -scheme "Free Ruler" test -only-testing:FreeRulerTests

Closes #248

[pascalpp]

• Drag visible rulers together when grouped #254 👈 (View in Graphite)
• Stagger new rulers from occupied defaults #253
• feature: Support Multiple Rulers #246 : 9 other dependent PRs (#238 , #255 , #256 and 6 others)
• main

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[pascalpp]

[codex reviewer] Reviewed the grouped-drag sync change. No blocking feedback from me; the manager snapshots visible ruler frames at drag start, applies the drag offset only to visible peers, and persists the updated set through the manager state notification path.