Resolves stdlib-js/metr-issue-tracker#54.

Description

What is the purpose of this pull request?

This pull request:

• Deletes legacy ESLint configuration files superseded by eslint.config.cjs (PR 12 of the migration plan).
• Removes .eslintrc.js, .eslintignore, per-target configs (benchmarks, examples, tests), and the overrides module.
• Inlines the restricted syntax config directly in eslint.config.cjs.
• Keeps etc/eslint/.eslintrc.js (consumed by typescript.js for base rule definitions), .eslintrc.markdown.js (consumed by remark plugin), and .eslintrc.typescript*.js files for now.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: migrate to ESLint v9 metr-issue-tracker#54

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

Stacked on #10973.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

• Yes
• No

If you answered "yes" above, how did you use AI assistance?

• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding

Disclosure

This PR was written primarily by Claude Code.

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@stdlib-js/reviewers