ast: add Node#deconstruct, fix hash

[apiology]

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

Problem:

Steep mistypes AST::Node#hash and lacks deconstruct:

# test.rb:17:9: [error] Cannot pass a value of type `::String` as an argument of type `::Integer`
Integer! node1.hash
# test.rb:28:14: [error] Type `::AST::Node` does not have method `deconstruct`
Array!  node1.deconstruct

Nodes used as hash keys or in array patterns get wrong or missing types.

Solution:

Type hash as Integer and add deconstruct: () -> Array[untyped], matching AST::Node in ast v2.4.3, where hash is [@type, @children, self.class].hash and deconstruct returns [type, *children].

[github-actions]

@apiology Thanks for your contribution!

Please follow the instructions below for each change.
See also: https://github.com/ruby/gem_rbs_collection/blob/main/docs/CONTRIBUTING.md

Available commands

You can use the following commands by commenting on this PR.

• /merge: Merge this PR if CI passes

---

ast

You changed RBS files for an existing gem.
You need to get approval from the reviewers of this gem.

@pocke, @kozy4324, please review this pull request.
If this change is acceptable, please make a review comment including APPROVE from here.

After that, the PR author or the reviewers can merge this PR.
Just comment /merge to merge this PR.

[kozy4324]

APPROVE

[github-actions]

Thanks for your review, @kozy4324!

@apiology, @kozy4324 This PR is ready to be merged.
Just comment /merge to merge this PR.

[apiology]

/merge