Upgrade @eslint/js 9.39.4 → 10.0.1

# Upgrade @eslint/js 9.39.4 → 10.0.1 (major)

Dependabot PR #7811. Dev dependency (`devDependencies`, `^9.39.4`); imported in `eslint.config.mjs` as `js`, used via `js.configs.recommended`. Pulled out of the weekly Dependabot slot per the major-version process — needs an owner and verification, not a batch merge.

## Compatibility pre-check

- ⚠️ `@eslint/js@10.0.1` declares `peerDependencies: { eslint: '^10.0.0' }` — our `eslint` core is pinned `^9.39.4` (resolved 9.39.4). This is the key mismatch: @eslint/js 10 requires ESLint 10, so the core `eslint` must bump in lockstep (latest is 10.8.0). Do not merge this PR alone.
- ✅ Node engines: @eslint/js 10 requires `^20.19.0 || ^22.13.0 || >=24`, same as ESLint 10 core; Node 24 dev default satisfies it.

## Breaking changes to review

- ESLint 10 removes legacy `.eslintrc` support (flat config only) — we already use flat config (`eslint.config.mjs`), so likely unaffected but confirm.
- `eslint:recommended` ruleset updated — previously passing code may now fail lint.
- Config objects gain a `name`; JSX reference tracking enabled; `Program` range spans entire source; minimatch v10; jiti ≥ 2.2.0.
- Removed deprecated `SourceCode` methods, rule context methods, `LintMessage#nodeType` / `TestCaseError#type`.

## To do before merge

- [ ] Coordinate with an ESLint 10 core bump (`eslint` → `^10.0.0`); both must land together. Run `npm run lint` after.
- [ ] Read the ESLint 10 migration guide and reconcile with eslint.config.mjs.

## Refs

- Branch: `dependabot/npm_and_yarn/eslint/js-10.0.1`
- PR: #7811
- Upstream: https://github.com/eslint/eslint/releases/tag/v10.0.0

Start with eslint.config.mjs and the ESLint 10 migration guide, then inspect the dependency declarations for the coordinated eslint core and @eslint/js bump. The change is done when both major-version dependencies are compatible, the flat configuration remains valid, and npm run lint passes.

Written by the indexing model from the issue text.