feat(ShannonEntropy): add Shannon Entropy BoxSource

[XiaoXiaoSN]

Box Source: Shannon Entropy (Analyze)

Adds the Shannon Entropy box source to Magic Box. It is disabled by default.

Details:

• Category (Kind): Analyze
• Tag: #
• Default Input: aaaabbbbcccd ::entropy

Options:

• ::entropy, ::shannon

Description:

Compute the Shannon entropy (bits per symbol) of the input text.

Usage Examples:

• Input:

aaaabbbbcccd ::entropy

• Output Box (Shannon Entropy):

Entropy: 1.855 bits/symbol
Length: 12 symbols
Unique Symbols: 4
Total Bits: 22

[XiaoXiaoSN]

Linting/testing failed on this branch.

Error details:

Please fix the linting and testing issues and ensure 'bun run lint' and 'bun test run' pass.

[XiaoXiaoSN]

This PR is ready to merge!