Linter: Implement erb-no-unused-expressions rule

[marcoroth]

Disallow expressions inside silent ERB tags (<% %>) whose return values are discarded. Writing expressions like <% @user.name %> or <% helper_method(arg) %> evaluates the expression but discards the result, making the line functionally useless.

This rule detects and warns about silent ERB tags containing:

• Method calls without blocks
• Instance variable reads (@user)
• Class variable reads (@@count)
• Global variable reads ($global)
• Constant reads (CONSTANT, Foo::Bar)

[pkg-pr-new]

npx https://pkg.pr.new/@herb-tools/formatter@1531

npx https://pkg.pr.new/@herb-tools/language-server@1531

npx https://pkg.pr.new/@herb-tools/linter@1531

commit: 769d2d8

[github-actions]

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_{🌱 Grown from commit 769d2d8}

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✅ Preview deployment has been cleaned up.

[brunoprietog]

This could result in some false positives, such as when using the turbo_refreshes_with helper, which doesn't require <%=.

[marcoroth]

Thanks @brunoprietog great catch! I opened #1586 to allow for those Turbo methods that have side effects 🙌🏼