feat: 0.2.0 — CLI, per-category operator specs, round-trip property

[ronaldtse]

Summary

0.2.0 — adds a CLI, per-category operator specs, and a round-trip property spec that caught 3 real serializer bugs.

New surface:

• Postscript.parse(source), Postscript.serialize(program, **opts), Postscript.tokenize(source) — top-level convenience API.
• exe/postscript CLI: parse INPUT, serialize INPUT [OUTPUT], tokenize INPUT, version.
• 13 per-category operator spec files (one per PLRM chapter).
• Round-trip property spec covering 6 representative PS programs + BoundingBox + HiResBoundingBox.

Bugs found by the property spec (all fixed):

1. Serializer always appended showpage even if the body already contained one — accumulated duplicates on each round-trip.
2. Serializer had per-operator emit_<keyword> methods that inlined operands, but the parser ALSO puts operands in body as standalone literal statements → each round-trip doubled the literal count.
3. Serializer didn't emit %%HiResBoundingBox even when the header had it.

Other:

• Added missing consumes/produces declarations to all Boolean ops and Transformations::Matrix.
• # frozen_string_literal: true on every .rb file.
• Initial CHANGELOG.md, LICENSE, .gitignore, .rubocop.yml.
• .github/workflows/{rake,release}.yml — CI + trusted-publishing release.

Test plan

• bundle exec rspec — 149 examples, 0 failures
• Round-trip property holds for all 6 fixtures
• CLI works: bundle exec ruby exe/postscript version → postscript 0.1.0
• bundle exec rake build produces pkg/postscript-0.1.0.gem
• Live: trigger release workflow with next_version=minor after merge; expect tag v0.2.0 + postscript-0.2.0.gem on RubyGems

After merge

gh workflow run release.yml -f next_version=minor

RubyGems trusted publisher must be configured at https://rubygems.org/gems/postscript/trusted_publishers with:

• Repository: claricle/postscript
• Workflow filename: rubygems-release.yml
• Workflow repository owner: metanorma
• Workflow repository name: ci