chore: upgrade ESLint to v10 with flat config

[brunoborges]

Summary

Upgrades ESLint from 8.57.0 → 10.5.0. ESLint 10 removes support for the legacy .eslintrc format entirely, so this migrates the configuration to the new flat config (eslint.config.mjs).

This supersedes the standalone Dependabot bump in #1022, which could not work on its own: bumping eslint to 10 without coordinating the @typescript-eslint upgrade and the flat-config migration triggers an ERESOLVE peer conflict (the old @typescript-eslint/eslint-plugin caps eslint at ^9) and leaves the action with an unsupported .eslintrc.js.

Changes

• Bump eslint 8.57.0 → 10.5.0 and eslint-plugin-jest → 29.15.2.
• Replace the legacy @typescript-eslint/eslint-plugin + @typescript-eslint/parser pair with the typescript-eslint meta-package (8.62.0), which supports ESLint 10.
• Replace the deprecated, unmaintained eslint-plugin-node (broken on ESLint 9+) with its maintained fork eslint-plugin-n (18.1.0). The only rule in use, node/no-extraneous-import, becomes n/no-extraneous-import.
• Add @eslint/js (10.0.1) and globals (17.7.0), now required by flat config.
• Translate .eslintrc.js → eslint.config.mjs and .eslintignore → the flat-config ignores, preserving all existing rules and the test-file overrides.
• Update the lint / lint:fix scripts to invoke eslint directly (flat config is auto-detected; the --config ./.eslintrc.js flag is removed).

Behavior preservation

• preserve-caught-error (new in ESLint 10's recommended set) is explicitly disabled to keep the previous lint behavior. Adopting it requires attaching an Error cause (ES2022 target) and is left as a follow-up.
• Only dev/lint dependencies change. Runtime dependencies are frozen at their main versions, so the built dist/ output is byte-for-byte unchanged (no dist/ diff in this PR).

Validation

• ✅ npm ci reproduces the lockfile
• ✅ npm run lint (ESLint 10 flat config) passes clean
• ✅ npm run format-check passes
• ✅ npm run build — dist/ identical to main
• ✅ npm test — 762/763 (the one failure is a sandbox network error unrelated to this change)
• ✅ npm audit --audit-level=high — no high-severity advisories

Note on auto-sync

.eslintrc.js was previously auto-synced from actions/reusable-workflows. Upstream has not yet published a flat config, so this migration intentionally deviates from that auto-sync until upstream catches up.

[Copilot]

Pull request overview

This PR upgrades the repository’s linting toolchain to ESLint v10 and migrates from legacy .eslintrc to the flat config format (eslint.config.mjs), along with the necessary ecosystem/plugin upgrades to maintain compatibility.

Changes:

• Upgrade ESLint to ^10.5.0 and adjust related lint dependencies (TypeScript ESLint via typescript-eslint, replace eslint-plugin-node with eslint-plugin-n, add @eslint/js and globals).
• Replace .eslintrc.js and .eslintignore with eslint.config.mjs using flat config and equivalent ignores/overrides.
• Update lint / lint:fix npm scripts to run ESLint without explicitly specifying the legacy config file.

Show a summary per file

File	Description
package.json	Updates lint scripts and devDependencies to ESLint 10 + flat-config-compatible plugins/packages.
package-lock.json	Lockfile updates reflecting the new ESLint/tooling dependency graph.
eslint.config.mjs	Introduces the flat ESLint configuration with ignores, TS + Jest setup, and updated n/ rule usage.
.eslintrc.js	Removes the legacy ESLint configuration (no longer supported in ESLint 10).
.eslintignore	Removes legacy ignore file in favor of flat config ignores.

Copilot's findings

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• Files reviewed: 4/5 changed files
• Comments generated: 1