Scaffold opencode-rails gem structure

- opencode-rails.gemspec (Ruby >= 3.2, MIT)
  - runtime: opencode-ruby ~> 0.0.1.alpha1
  - runtime: activerecord/activestorage/activesupport >= 7.1, < 9.0
    Per-sublibrary deps (not the rails umbrella) so host apps don't
    pull in ActionMailer/ActionCable/ActionView just to use this gem.
- lib/opencode-rails.rb (umbrella; requires opencode-ruby then leaves
  then session/turn)
- lib/opencode/rails/version.rb (Opencode::Rails::VERSION = 0.0.1.alpha1)
- Gemfile (sibling-path pull of opencode-ruby for local dev)
- Rakefile, .gitignore

Source files will be ported in the next commit.

.gitignore

@@ -0,0 +1,8 @@
+*.gem
+.bundle/
+Gemfile.lock
+pkg/
+tmp/
+.ruby-version
+.byebug_history
+coverage/

Gemfile

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+source "https://rubygems.org"
+
+# opencode-ruby is the underlying wire client. During alpha both gems
+# evolve in lockstep; the gemspec pins a release version, but for local
+# dev we pull from the sibling working copy so changes in opencode-ruby
+# are picked up without a release cycle.
+if File.exist?(File.expand_path("../opencode-ruby", __dir__))
+  gem "opencode-ruby", path: File.expand_path("../opencode-ruby", __dir__)
+end
+
+gemspec

Rakefile

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+# frozen_string_literal: true
+
+require "bundler/gem_tasks"
+require "rake/testtask"
+
+Rake::TestTask.new(:test) do |t|
+  t.libs << "test"
+  t.libs << "lib"
+  t.test_files = FileList["test/**/*_test.rb"]
+end
+
+task default: :test

lib/opencode-rails.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+# opencode-rails — Production Rails integration for OpenCode.
+#
+# Loads the wire-level primitives from opencode-ruby, then layers on the
+# AR-coupled session/turn/artifact stack. Caller-facing namespace stays
+# flat at `Opencode::*` (no `Opencode::Rails::Session` etc.) so this gem
+# can drop into any app that already uses opencode-ruby with zero
+# rename work.
+
+require "opencode-ruby"
+
+require "active_support/core_ext/object/blank"
+require "active_support/core_ext/object/try"
+require "active_support/core_ext/hash/keys"
+require "active_support/core_ext/string/inflections"
+
+require_relative "opencode/rails/version"
+require_relative "opencode/error_reporter"
+
+# Tier 4 leaves (no deps on other rails-gem files)
+require_relative "opencode/sandbox_file"
+require_relative "opencode/sandbox"
+require_relative "opencode/transform"
+require_relative "opencode/impostor"
+require_relative "opencode/artifact"
+require_relative "opencode/message_artifacts"
+require_relative "opencode/uploaded_files_prompt"
+require_relative "opencode/tool_display"
+require_relative "opencode/exchange"
+
+# Tier 3 (depend on the leaves above)
+require_relative "opencode/session"
+require_relative "opencode/turn"
+
+module Opencode
+end

lib/opencode/rails/version.rb

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+# frozen_string_literal: true
+
+module Opencode
+  module Rails
+    VERSION = "0.0.1.alpha1"
+  end
+end

opencode-rails.gemspec

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+# frozen_string_literal: true
+
+require_relative "lib/opencode/rails/version"
+
+Gem::Specification.new do |spec|
+  spec.name          = "opencode-rails"
+  spec.version       = Opencode::Rails::VERSION
+  spec.authors       = ["Ajay Krishnan"]
+  spec.email         = ["ajay@krishnan.ca"]
+
+  spec.summary       = "Production-grade Rails integration for OpenCode."
+  spec.description   = <<~DESC
+    Rails companion to opencode-ruby. ActiveRecord-aware session lifecycle
+    (idempotent ensure!/recreate!/abort! with row-level locks), a Turn
+    orchestrator that drives the Reply state machine + handles
+    session-not-found recovery, an artifact pipeline backed by
+    ActiveStorage, sandbox seeding, and tool-display value objects for
+    Turbo Stream broadcasts. Drop into any Rails 7.1+ app that wants
+    production-grade OpenCode streaming without rolling your own
+    boilerplate.
+  DESC
+  spec.homepage      = "https://gitea.krishnan.ca/ajaynomics/opencode-rails"
+  spec.license       = "MIT"
+  spec.required_ruby_version = ">= 3.2.0"
+
+  spec.metadata["source_code_uri"] = spec.homepage
+  spec.metadata["changelog_uri"]   = "#{spec.homepage}/src/branch/main/CHANGELOG.md"
+  spec.metadata["bug_tracker_uri"] = "#{spec.homepage}/issues"
+
+  spec.files = Dir.glob("lib/**/*.rb") +
+               %w[README.md LICENSE CHANGELOG.md opencode-rails.gemspec]
+  spec.require_paths = ["lib"]
+
+  # The opencode-ruby gem provides the wire-level Client + Reply primitives
+  # this gem builds on. Versions are kept in lockstep during the alpha
+  # phase; will relax to a looser pessimistic pin once both gems stabilize.
+  spec.add_runtime_dependency "opencode-ruby", "~> 0.0.1.alpha1"
+
+  # Rails sub-libraries used at runtime. Depending on these individually
+  # (instead of the `rails` umbrella) avoids forcing host apps to load
+  # ActionMailer, ActionCable, ActionView, etc. just to use this gem.
+  spec.add_runtime_dependency "activerecord",  ">= 7.1", "< 9.0"
+  spec.add_runtime_dependency "activestorage", ">= 7.1", "< 9.0"
+  spec.add_runtime_dependency "activesupport", ">= 7.1", "< 9.0"
+
+  spec.add_development_dependency "minitest", "~> 5.20"
+  spec.add_development_dependency "rake", "~> 13.0"
+end