feat(selection): support multi-range selection with drag previews

[ghiscoding]

## Summary

This PR selectively ports the multi-range selection functionality and related fixes from upstream PRs #2748, #2759, and #2777.

## Why

Users can select multiple non-contiguous cell or row ranges using Excel-like Ctrl/Cmd interactions.

## Changes

• Added the enableMultiSelection selection option.
• Added SelectionModel.setOptions().
• Added Ctrl/Cmd-click range toggling and rectangular range splitting.
• Added Ctrl/Cmd-drag range additions for cells and rows.
• Preserved existing ranges during live drag previews.
• Synchronized the active cell when selectActiveRow is disabled.
• Preserved gaps when copying non-contiguous ranges.
• Updated the draggable interaction to support selection-model options after initialization.
• Added and updated Cypress coverage and the Hybrid Selection Model example.

PR #2757 is intentionally excluded because Shift-click range extension is a separate scope.

## Validation

• Cypress E2E tests passed in Cypress UI/dev-watch mode.
• npx tsc --noEmit --incremental false
• npm run lint
• npm run build:prod
• git diff --check

## Comments

The changes are limited to the core SlickGrid selection behavior and related Vanilla example/test coverage.

The local npm run cypress:ci command could not be used for final validation because the browser process exits with code 132 in the current environment.

## AI / LLM assistance

• AI / LLM assistance used:
  • No
  • Yes
• If Yes:
  • which tool/model: OpenAI Codex / GPT-5
  • how was it used: Reviewed the upstream PRs, implemented the corresponding SlickGrid changes, added Cypress coverage, investigated test failures, and validated the implementation.

## Checklist

• The changes are limited to only one scope.
• Tests were added or updated where appropriate.
• Documentation was updated where appropriate.