feat: add drill-down and deep select support to selection state

[MinCrohn]

This update enhances the Selection System to provide library users with more control over navigating nested object structures. Two new options, drillDown and deepSelect, have been added to the SelectionState configuration.

1. Drill-down Selection (drillDown)

• Description: Allows users to "enter" nested groups step-by-step. When enabled, a double-click (or subsequent clicks) on a previously selected group will search for and select the specific child object located at the click point.

• User Experience: Instead of always selecting the top-most group, users can repeatedly click to drill into the exact component they wish to modify.

2. Deep Select (deepSelect)

• Description: Provides a shortcut to bypass standard selection units (like 'highestGroup'). When enabled, holding the Ctrl (Windows) or Meta/Cmd (Mac) key during a click will force the selection logic to target the lower-level 'grid' unit immediately.

• User Experience: Users can quickly select specific items within complex layouts without needing to navigate the group hierarchy manually.

---

How to Activate

You can enable these features by passing them as options when setting the selection state via the stateManager.

// Example: Activating drillDown and deepSelect in your Patchmap instance
patchmap.stateManager.setState('selection', {
  draggable: true,
  selectUnit: 'highestGroup', // Default behavior: select the top group
  
  // New Options
  drillDown: true,  // Enable drilling into groups on double-click
  deepSelect: true, // Enable Ctrl/Cmd + click to select grids directly
  
  onClick: (target) => {
    console.log("Selected Object:", target?.id);
  }
});

[gemini-code-assist]

Summary of Changes

Hello @MinCrohn, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the Selection System by introducing two powerful new features: drillDown and deepSelect. These additions provide library users with greater control and flexibility when interacting with complex, nested object structures. The changes aim to streamline the user experience by allowing more precise and efficient selection of elements within a hierarchical layout, reducing the need for manual navigation through parent groups.

Highlights

• Drill-down Selection: Introduced a drillDown option that allows users to navigate into nested groups step-by-step. When enabled, subsequent clicks on an already selected group will select deeper child objects at the click point.
• Deep Select: Added a deepSelect option which enables users to bypass standard selection units and directly select lower-level 'grid' units by holding the Ctrl (Windows) or Meta/Cmd (Mac) key during a click.
• Enhanced Selection Logic: Refactored the internal selection mechanism to support these new features, including modifications to object finding, parent traversal, and interaction state management.
• Documentation Updates: The README.md and README_KR.md files have been updated to include detailed descriptions and usage examples for the new drillDown and deepSelect configuration options.

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[gemini-code-assist]

Code Review

This pull request introduces drillDown and deepSelect functionalities to the selection system, which is a great enhancement for navigating complex object hierarchies. The implementation is well-structured, with good use of Symbols for states and a strategy pattern in getSelectObject. The refactoring of the SelectionState class, including the consolidation of clear methods and extraction of a default config, improves code clarity.

My main feedback is a critical point regarding the lifecycle management in SelectionState. The exit method now destroys _selectionBox, which could lead to runtime errors if state objects are reused. I've provided a suggestion to make the enter method more robust to handle this case.

Overall, this is a valuable feature addition with thoughtful implementation details.