`rbs prototype rb` generates wrong definitions for files including "#$"

rbs generates a definition that causes a syntax error if the file includes '#$'.

Steps to reproduce

$ cat foo.rb
class A
  X = '#$'
end

$ rbs prototype rb foo.rb > foo.rbs

$ cat foo.rbs
class A
  X: "\#$"
end

$ rbs parse foo.rbs
foo.rbs:2:5...2:6: Syntax error: unexpected token for simple type, token=`"` (ErrorToken)

System Information

$ ruby --version
ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [arm64-darwin21]

$ rbs --version
rbs 3.1.0

Notes

I report that the error did not occur in v2.5.1, but did occur in v2.6.0.

$ rbs _2.5.1_ parse foo.rbs

$ rbs _2.6.0_ parse foo.rbs
foo.rbs:2:5...2:6: Syntax error: unexpected token for simple type, token=`"` (ErrorToken)

Reproduce the issue with the shown rbs prototype rb foo.rb and rbs parse foo.rbs commands, then trace the prototype rb implementation and its tests. Add a regression case for a Ruby string containing '#$'; done means the generated definition parses successfully and preserves the intended value.