feat: add vk CLI alias for improved developer experience

[joedanz]

Summary

This PR adds vk as a shorter alias for the vibekit CLI command, allowing developers to use either vibekit or vk to invoke the CLI.

Changes

• Added vk alias to the bin configuration in root package.json
• Added vk alias to the bin configuration in packages/cli/package.json

Motivation

• Provides a shorter, more convenient command for frequent CLI usage
• Follows common CLI patterns where tools offer abbreviated aliases (e.g., kubernetes → k, docker-compose → dc)
• Improves developer experience without breaking existing workflows

Testing

• ✅ Built the CLI package successfully
• ✅ Verified both vibekit and vk commands are available in PATH
• ✅ Confirmed both commands execute correctly with --version flag

Usage

After this PR is merged, developers can use either:

vibekit init -a claude -p e2b
# or
vk init -a claude -p e2b

Both commands are functionally identical.

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