fix(content-explorer): add file selection validation callback

[devin-ai-integration]

Description

Add onSelection callback to ContentExplorer to allow developers to control or validate file selection before processing. This provides a way to prevent invalid selections based on custom criteria.

Changes

• Added onSelection prop that takes a callback function
• Callback receives selected items array and returns boolean
• Integrated with all selection methods (click, double-click, select-all)
• Added comprehensive test coverage
• Maintained backward compatibility

Testing

• Added unit tests for all selection methods
• Verified existing functionality not affected
• Tests passing: 9732 passed, 3 skipped

Link to Devin run: https://app.devin.ai/sessions/7d4bd4fe16a54373996b6398d5ff9b57

[devin-ai-integration]

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[devin-ai-integration]

Closing due to inactivity.