fix: align @vitest/coverage-v8 with vitest 4.0.18

[Copilot]

Dependabot bumped vitest to 4.0.18 but left @vitest/coverage-v8 at 4.0.16, causing peer dependency conflicts in CI.

Changes

• Bump @vitest/coverage-v8 from ^4.0.6 to ^4.0.18

The coverage plugin enforces strict peer dependency matching with vitest core. Version alignment resolves the ERESOLVE errors blocking the original dependency update.

Original prompt

Pull Request: #461

Please address the CI errors if possible

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[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	49.81%	402 / 807
🔵	Statements	50.48%	414 / 820
🔵	Functions	65.74%	71 / 108
🔵	Branches	49.38%	200 / 405

File Coverage

No changed files found.

Generated in workflow #393 for commit 357499a by the Vitest Coverage Report Action

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[Copilot]

Pull request overview

This PR resolves a peer dependency conflict that was blocking CI. When Dependabot bumped vitest to version 4.0.18 in PR #461, it left @vitest/coverage-v8 at an older version, causing ERESOLVE errors due to the coverage plugin's strict peer dependency requirements.

Changes:

• Bump @vitest/coverage-v8 from ^4.0.6 to ^4.0.18 to align with vitest 4.0.18

Reviewed changes

Copilot reviewed 1 out of 3 changed files in this pull request and generated no comments.

File	Description
package.json	Updates @vitest/coverage-v8 version from ^4.0.6 to ^4.0.18 in devDependencies
package-lock.json	Updates lockfile with new version, transitive dependencies (ast-v8-to-istanbul ^0.3.10), removes istanbul-lib-source-maps (no longer needed), and deduplicates nested node_modules entries