Preserve zero input in Node API

[vetrovk]

Fixes #2590.

This change preserves numeric 0 as valid input in the Node API instead of treating it as missing input.

Changes:

• preserve 0 in Node API input normalization
• preserve 0 in Dish construction
• add regression coverage for chef.toHex(0), chef.bake(0, ...), chef.ADD(0, ...), and new Dish(0)
• keep existing behavior for empty string and false

Validation:

• env PATH="/opt/homebrew/opt/node@24/bin:$PATH" npm ci
• env PATH="/opt/homebrew/opt/node@24/bin:$PATH" node --no-warnings --no-deprecation --openssl-legacy-provider tests/node/index.mjs
• env PATH="/opt/homebrew/opt/node@24/bin:$PATH" npm run testnodeconsumer
• env PATH="/opt/homebrew/opt/node@24/bin:$PATH" npm run lint
• git diff --check

Notes:

• Validation ran with Node v24.17.0 and npm 11.13.0.

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