Fix additions

[koppen]

Ie doing

Classlist.new("a b c") + Classlist.new("d e")

is the same as

Classlist.new("a b c") + Classlist::Add.new("d e")

and most notably doing

Classlist.new("a") + Classlist::Remove.new("a") + Classlist.new("b")

is the same as

Classlist.new("a") + Classlist::Remove.new("a") + Classlist::Add.new("b")

which it wasn't before.

Adding a "base" Classlist in that manner would merge it into the Remove
operation, effectively turning the statement into

Classlist.new("a") + Classlist::Remove.new("a b")

which is not the intended behavior

[Copilot]

Pull request overview

This PR fixes a bug where adding a plain Classlist instance to a chain of Classlist::Operations would incorrectly merge it into the last operation instead of treating it as an implicit Classlist::Add operation. The fix ensures consistent behavior whether you use Classlist.new("foo") or Classlist::Add.new("foo") when chaining operations.

Key changes:

• Added type conversion logic to treat plain Classlist instances as Classlist::Add operations when used with the + operator
• Added test coverage for the new behavior with both explicit Classlist::Add and implicit plain Classlist additions
• Fixed missing require statement for Classlist::Reset in the test file

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
lib/classlist.rb	Added logic to convert plain Classlist instances to Classlist::Add operations before processing in the + operator
test/classlist/test_operation.rb	Added missing Reset require statement and two new tests verifying the fix works correctly
CHANGELOG.md	Documented the bug fix in the Fixed section

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