Fix prepublishOnly hook by adding prettier formatting check

[Copilot]

The prepublishOnly hook was incomplete compared to the CI quality checks, potentially allowing packages to be published with formatting issues that would later fail CI.

Problem

The current prepublishOnly script only ran:

"prepublishOnly": "npm test && npm run lint:check"

However, the CI pipeline (test-ci) also includes prettier formatting checks:

"test-ci": "npm run lint:check && npm run prettier:check && jest unit --coverage && ..."

This mismatch could lead to a scenario where:

1. Developer makes changes locally
2. prepublishOnly hook passes (tests + linting)
3. Package gets published to npm
4. CI fails due to prettier formatting issues

Solution

Updated the prepublishOnly script to include prettier formatting validation:

"prepublishOnly": "npm test && npm run lint:check && npm run prettier:check"

Now the prepublishOnly hook enforces the same quality standards as CI:

• ✅ TypeScript definitions validity (tsd)
• ✅ Unit tests pass (jest unit)
• ✅ Code passes linting (eslint)
• ✅ Code is properly formatted (prettier)

This ensures that only properly formatted, tested, and linted code can be published to npm, maintaining consistency with the project's quality standards.

Fixes #279.

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