feat: change the scope to @webship-js/diffy-steps (#3)

[Natshah]

- "name": "@webship/diffy-steps",
+ "name": "@webship-js/diffy-steps",

Closes #3

@webship is the GitHub organisation for the whole Webship product family — the
Drupal distribution, the 14 web* modules, the theme, the patch metapackages,
the project templates. Almost none of that is JavaScript and none of it is on
npm. This package is a plugin for the webship-js harness and is useful with
nothing else, so the scope now names what it plugs into.

It also reads better where it matters — a consumer's cucumber.js:

require: [
  'node_modules/webship-js/tests/step-definitions/**/*.js',              // core
  'node_modules/@webship-js/diffy-steps/tests/step-definitions/**/*.js', // this plugin
],

version stays 2.0.0, publishConfig.access stays public.

Changed

File	What
package.json	name
README.md	heading, prose, install, require: path
docs/README.md	heading, intro
tests/step-definitions/README.md	install, require: path, cp, npm uninstall
tests/step-definitions/diffy.steps.js	header comment
package-lock.json	regenerated

Timing

Nothing is published, so this is free — no deprecation, no redirect, no consumer
migration. That window closes at first publish, which is the argument for
settling the scope now rather than after.

Namespace caveat — worth knowing before creating the org

An npm package named webship-js already exists (the harness). As of this
PR there is no org or reserved scope of that name — registry.npmjs.org/-/org/webship-js
returns 404 and @webship-js/diffy-steps is unclaimed — but whether npm permits
an org whose name collides with an existing package name is only settled when
you try to create it. I could not verify that ahead of time.

If npm rejects webship-js as an org name, the fallbacks are to revert to
@webship or pick a third scope; either way #3 should record the outcome.
Neither publish blocker from before has moved: npm whoami still reports
ENEEDAUTH, and no org exists yet.

Test notes

• npm pack --dry-run → @webship-js/diffy-steps@2.0.0, filename webship-js-diffy-steps-2.0.0.tgz, same 5-file payload.
• Suite re-run after the change: 6 scenarios / 37 steps passing against the mock Diffy API.
• No @webship/ references remain anywhere in the tree.

Knock-on outside this repo: webship-js CLAUDE.md §2.6 on 2.0.x names the
@webship/... require path and needs the same correction — separate issue and
PR so this one stays single-purpose.

AI-Generated: Yes (applied the rescope and updated every reference; reviewed by
Rajab Natshah.)

Checkpoints

• File an issue about this project
• Addition/Change/Update/Fix to this project
• Testing to ensure no regression
• Automated unit/functional testing coverage
• Developer Documentation support on feature change/addition
• User Guide Documentation support on feature change/addition
• Accessibility and Readability
• Reviewed by a human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Update Release Notes
• Release