Fix equality for types whose name cannot be rooted

[apiology]

Claude: This PR was written by Claude Code on behalf of @apiology.

ComplexType::UniqueType#eql? compares the raw @rooted ivar on the left against the rooted? reader on the right, and rooted? is !can_root_name? || @rooted. For a name that cannot be rooted — undefined is the case that arises in practice — the reader returns true while the ivar is false, so that clause is permanently false and an undefined type is not equal even to itself. Anything relying on Ruby equality of types rather than tag-string equality silently treats two undefined types as distinct.

a = Solargraph::ComplexType.parse('undefined').items.first
a.eql?(a)                      # => false  (want true)

x = Solargraph::ComplexType::UniqueType.new('undefined', rooted: false)
y = Solargraph::ComplexType::UniqueType.new('undefined', rooted: false)
[x, y].uniq.length             # => 2      (want 1)

p = Solargraph::ComplexType::UniqueType::UNDEFINED
q = p.erase_parameters         # passes rooted: rooted?, storing the opposite flag
[p.eql?(q), q.eql?(p)]         # => [false, true]  asymmetric, and p.hash != q.hash

Compare rooted? on both sides rather than both raw ivars: where a name can be rooted the two spellings are identical, and where it cannot, rootedness carries no meaning, so two such types are the same type whichever flag built them. hash moves with it, since it read @rooted and would otherwise leave that erase_parameters pair equal but hashed differently.