Add JSHint configuration scoped to the repo to avoid ancestor-config false positives

[westonruter]

Summary

When this repo is checked out inside a wordpress-develop checkout (a common local setup), the IDE's JSHint inspection has no .jshintrc in this repo to anchor on, so it walks up the directory tree and falls through to wordpress-develop's ancestor .jshintrc. That ancestor config assumes a browser environment, an older ECMAScript version, and WP-core's operator-at-line-end style — none of which match this repo's Prettier-formatted, modern, mixed Node/browser JavaScript. The result is a stream of false-positive JSHint warnings across the repo's JS files.

This PR adds a JSHint configuration scoped to this repo that shadows the ancestor and silences those false positives, while still doing real linting (genuinely undefined globals and unused vars are still flagged).

This is purely IDE/tooling configuration — this repo uses ESLint (@wordpress/scripts) for its actual JS linting and does not run JSHint in CI. The configuration simply mirrors, in JSHint terms, the Node-vs-browser split that eslint.config.js already encodes.

What's included

• .jshintrc (root) — Node environment for the root config files, bin/, and tools/ tooling. Enables laxbreak (Prettier puts ?/: at line starts), loopfunc, and the fetch/AbortController globals Node 18+ provides but JSHint's stale node set omits.
• plugins/.jshintrc — Browser environment for the shipped client scripts. Adds devel (console) plus the modern globals the stale browser set omits: ResizeObserver, requestIdleCallback/cancelIdleCallback, structuredClone, CompressionStream, crypto — and name, so the ES-module export const name stops tripping the read-only-global redefinition warning.
• .jshintignore — Skips generated/minified output (build/, dist/, **/*.min.js) and vendored/installed dependencies.
• plugins/auto-sizes/tests/e2e/specs/improve-calculate-sizes.spec.js — Gets an inline /* jshint node: true */ directive because it's a Node CommonJS Playwright test living under the browser-oriented plugins/ tree, so it needs the Node globals layered on top of the browser config.

Testing

Ran JSHint (via the wordpress-develop checkout's node_modules/.bin/jshint, auto-discovering these configs) across all tracked, non-generated JS files in the repo: 0 warnings. A probe confirmed the new configs are the ones being applied — JSHint recognizes the added globals (e.g. ResizeObserver) yet still flags genuinely undefined identifiers and unused variables, so linting integrity is preserved.

🤖 Generated with Claude Code

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: westonruter <westonruter@git.wordpress.org>
Co-authored-by: b1ink0 <b1ink0@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[westonruter]

When you have the performance repo checked out in wordpress-develop at src/wp-content/plugins/performance, this prevents PhpStorm from surfacing errors like the following in bin/commands/versions.js:

[b1ink0]

LGTM