simplify deps & dev deps + node 22

[MoOx]

Breaking changes, but node <= 20 are at EOL.

[Copilot]

Pull request overview

This PR aims to simplify the development toolchain by removing Mocha/Chai/ESLint, migrating tests to Node’s built-in node:test runner, and switching linting to oxlint.

Changes:

• Replace Mocha/Chai-based test setup with node:test + node:assert (with a small compatibility shim).
• Replace ESLint with oxlint, and remove ESLint config files.
• Minor refactors/cleanups in tests and URL/path handling (regex simplifications, startsWith, endsWith, slash normalization).

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/type/inline.js	Updates assertions and simplifies a custom filter function.
test/type/copy.js	Cleans up regex/string escaping for URL path expectations.
test/setup.js	Migrates test harness from Chai/Mocha globals to node:test + node:assert.
test/.eslintrc.js	Removes test-specific ESLint config.
src/lib/paths.js	Small simplifications in path normalization and URL checks.
package.json	Drops mocha/chai/eslint, adds oxlint, updates test/lint scripts, bumps postcss-import.
package-lock.json	Updates lockfile to reflect new dev dependency set.
.eslintrc.js	Removes root ESLint configuration.

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