Replace ember-engines.com references with GitHub repository URL

[Copilot]

The ember-engines.com domain has been lost and now points to an unrelated AI content site. Updated all references to use the GitHub repository URL instead.

Changes

• Updated assertion message in LinkTo component validation
• Updated corresponding test assertion strings in routing tests

// Before
'See https://ember-engines.com/docs/links for more info.'

// After  
'See https://github.com/ember-engines/ember-engines/ for more info.'

Files changed:

• packages/@ember/-internals/glimmer/lib/components/link-to.ts
• packages/@ember/-internals/glimmer/tests/integration/components/link-to/routing-angle-test.js
• packages/@ember/-internals/glimmer/tests/integration/components/link-to/routing-curly-test.js

Original prompt

Find and replace any references to 'ember-engines.com' throughout the repository, including documentation comments and test assertion strings, with 'https://github.com/ember-engines/ember-engines/'. Where 'ember-engines.com' is used as a link, update the href to point to the GitHub repository. Where it appears in documentation or assertions, update the text accordingly. Add a note to the PR description that this is due to the domain having been lost and now belonging to an unrelated AI content site.

This pull request was created from Copilot chat.

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