feat: implement safe deletion with trash/recycle bin suppor

[5angar1us]

Summary: Enhanced existing remove and manage commands with safer deletion behavior using system trash/recycle bin as default instead of permanent deletion.

What: Added safe deletion support to remove and manage commands using system trash/recycle bin as default, with --force flag for permanent deletion.

Why:

• I deleted my local skills and the only thing that saved me was that I had backups. This change adds a safety layer to prevent accidental loss of skills.

Implementation:

• Added safeDelete() function in src/utils/trash.ts using trash package for cross-platform support
• Added --force flag to both manage and remove commands for permanent deletion
• Extended DeleteOptions interface with permanent?: boolean field
• Updated CLI interface to handle the --force option
• Uses the trash package to move to the trash by default
• Updated README.md to reflect new functionality and usage

Testing:

• All existing tests pass (11/11)
• Added 5 comprehensive tests for safeDelete function
• Total: 16/16 tests passing
• Cross-platform testing with platform-aware test paths
• Tests verify logic, not platform-specific behavior

An important note from the author of trash:

• The Linux implementation is not very good and not maintained. Help welcome. If no one steps up to help maintain it, I will eventually remove Linux support.
  From the project's Readme

Usage:

# Interactive management (uses trash by default)
openskills manage

# Interactive management with permanent deletion
openskills manage --force

# Non-interactive removal (uses trash by default)
openskills remove my-skill

# Non-interactive permanent deletion
openskills remove my-skill --force