Fix linting errors and add development tooling

[alexgrozav]

Summary

• Fix no-new-array lint error in scanner.ts by using Array.from instead of new Array()
• Mark intentional unused variables in test fixtures with eslint-disable-next-line comments
• Add typecheck script using tsc --noEmit for TypeScript validation
• Expand .gitignore with standard entries (coverage, logs, env files, OS artifacts)

Test plan

• Verify linting passes: npm run lint
• Verify tests pass: npm run test
• Verify typecheck passes: npm run typecheck

[Copilot]

Pull request overview

This PR focuses on resolving linting issues and improving developer tooling for the TypeScript codebase, including adding a dedicated type-check command and tightening generated-file ignores.

Changes:

• Replace new Array(len) in stripComments to satisfy linting (no-new-array).
• Silence intentional no-unused-vars violations in test fixtures via eslint-disable-next-line.
• Add typecheck script (tsc --noEmit) and expand .gitignore for common generated artifacts.

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
vitest.config.ts	Consolidates coverage exclude configuration formatting.
src/scanner.ts	Updates result buffer initialization in stripComments to address lint rule.
src/tests/fixtures/strings/entry.ts	Suppresses unused-vars warnings for fixture-only constants.
src/tests/fixtures/mixed/entry.ts	Suppresses unused-vars warnings for fixture-only imports/expressions.
src/tests/fixtures/externals/local.ts	Suppresses unused-vars warning for intentionally unused import.
src/tests/fixtures/externals/entry.ts	Suppresses unused-vars warnings for intentionally unused external imports.
package.json	Adds typecheck script for tsc --noEmit.
.gitignore	Ignores common build, coverage, log, and env artifacts.

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[Copilot]

Array.from({ length: len }) eagerly creates a dense array of len undefined values, which adds an extra O(n) initialization pass and more memory churn compared to the previous sparse new Array(len). Since result is fully assigned in the loop anyway, consider keeping the array sparse without using the Array constructor (e.g., initialize as [] and set result.length = len) to preserve performance while satisfying no-new-array.

Suggested change

	const result: string[] = Array.from<string>({ length: len });
	const result: string[] = [];
	result.length = len;