`stree write` turns correct code into incorrect code for method call with mix of keyword types

[Bradley Buda]

When calling a method with multiple keyword values, where one of the keywords is "static" and another is "dynamic" (for lack of better terms), stree write emits bad code. Possibly related to #419 but I'm not 100% certain. A minimal example:

Input

def search(keyword:, author: nil, category: nil)
  # implementation elided
end

keyword = 'Ruby'
facet = :author
value = 'Matz'

search(facet => value, keyword:)

Formatted Output

def search(keyword:, author: nil, category: nil)
  # implementation elided
end

keyword = "Ruby"
facet = :author
value = "Matz"

search(facet => value, :keyword =>)

This is with the latest released version (6.2.0). Here's a full transcript of the commands I ran, just in case I missed something:

% cat before.rb
def search(keyword:, author: nil, category: nil)
  # implementation elided
end

keyword = 'Ruby'
facet = :author
value = 'Matz'

search(facet => value, keyword:)

% cp before.rb after.rb

% bundle exec stree version
6.2.0

% bundle exec stree write after.rb
after.rb 2ms

% cat after.rb
def search(keyword:, author: nil, category: nil)
  # implementation elided
end

keyword = "Ruby"
facet = :author
value = "Matz"

search(facet => value, :keyword =>)

% ruby before.rb

% ruby after.rb
after.rb: --> after.rb
syntax error, unexpected ')'
> 1  def search(keyword:, author: nil, category: nil)
> 3  end
> 5  keyword = "Ruby"
> 6  facet = :author
> 7  value = "Matz"
> 9  search(facet => value, :keyword =>)

after.rb:9: syntax error, unexpected ')' (SyntaxError)
...ch(facet => value, :keyword =>)
...                              ^

% ruby --version
ruby 3.2.3 (2024-01-18 revision 52bb2ac0a6) [arm64-darwin23]