chore: use testcontext for test:node-test, batch 1

[Uzlopak]

A small batch of test/node-test/ test files

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[Copilot]

Pull Request Overview

This pull request refactors test files in the test/node-test/ directory to use Node.js's native testcontext instead of the external tspl library, representing the first batch of conversions.

• Migration from @matteo.collina/tspl to Node.js native test context and assertions
• Restructuring tests to use describe/beforeEach/afterEach patterns where applicable
• Switching from external assert module to test context assertions

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/node-test/validations.js	Converts from single test with tspl to describe block with individual tests using test context
test/node-test/util.js	Replaces assert module with test context assertions
test/node-test/unix.js	Migrates from tspl to test context with proper server cleanup
test/node-test/tree.js	Removes assert module dependency in favor of test context
test/node-test/large-body.js	Simple migration from assert module to test context
test/node-test/debug.js	Converts from tspl async pattern to callback-based test context

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