Fix _lastId variable collision when multiple keyborg bundles are loaded

[Copilot]

Problem

When multiple bundles of the keyborg package are loaded on the same site, each bundle maintains its own file-scoped _lastId variable. This leads to ID conflicts and incorrect behavior as different bundles can generate overlapping IDs for KeyborgCore and Keyborg instances.

// Before: Each bundle has its own _lastId counter
let _lastId = 0; // Bundle A starts at 0
let _lastId = 0; // Bundle B also starts at 0
// This causes ID collisions!

Solution

Move the _lastId counter to the shared window.__keyborg object so all bundles use the same ID sequence, ensuring unique IDs across all instances regardless of which bundle created them.

Changes Made

• Extended WindowWithKeyborg interface to include _lastId: number
• Created getNextId() helper function that manages the shared ID counter on window.__keyborg._lastId
• Replaced all ++_lastId usages with calls to getNextId(win)
• Removed the file-scoped _lastId variable
• Added backward compatibility for older bundles that don't have the _lastId property

Compatibility Features

The fix ensures compatibility between fixed and unfixed bundles:

• If window.__keyborg doesn't exist, initializes it with _lastId: 0
• If window.__keyborg exists but lacks _lastId, adds it starting from 0
• Preserves existing _lastId value when creating new __keyborg objects
• Works seamlessly with both old and new bundle versions on the same page

Testing

• ✅ Build passes with no TypeScript errors
• ✅ Linting passes with no issues
• ✅ ID generation works correctly across multiple instances
• ✅ Backward compatibility verified with simulated older bundle scenarios
• ✅ Shared counter properly increments and avoids collisions

This change resolves the multiple bundle issue while maintaining full backward compatibility.

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