fix: typecheck and add v8 coverage

[pwlmc]

• Added @vitest/coverage-v8 as a development dependency in package.json to enable V8-based code coverage reporting for tests.
• Updated tsconfig.json to no longer explicitly exclude test files (*.spec.ts, *.test.ts)

[Copilot]

Pull request overview

This PR enables TypeScript type-checking for test files and adds V8-based code coverage support to the imghash package.

• Removed test file exclusions from tsconfig.json to enable TypeScript type-checking of test files
• Added @vitest/coverage-v8 dependency for V8-based coverage reporting
• Updated package-lock.json with all necessary transitive dependencies

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/imghash/tsconfig.json	Removed **/*.spec.ts and **/*.test.ts from exclude array to enable type-checking of test files
packages/imghash/package.json	Added @vitest/coverage-v8@^4.0.14 as a development dependency
package-lock.json	Added coverage-v8 and related dependencies (babel, istanbul libs, magicast, obug, etc.) and updated vitest-related packages to 4.0.14

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