Code review actions: rename version file, drop Gemfile conditional, tighten gemspec, switch URLs to GitHub

Three tightly-coupled cleanups from the Tobi+Sandi review:

1. Rename lib/opencode/rails/version.rb -> lib/opencode/rails_version.rb
   (Sandi S1: file path was lying about its contents — the file defines
   Opencode::RAILS_VERSION, NOT Opencode::Rails::VERSION). Updated the
   require_relative in opencode-rails.gemspec and lib/opencode-rails.rb
   to match. Removed the now-empty lib/opencode/rails/ directory.

2. Drop the 'if File.exist?(...) gem opencode-ruby, path: ...' Gemfile
   conditional (Tobi T2 / Sandi S4: Bundler behavior must not depend on
   filesystem state). The dev-time sibling-repo override is now
   documented in CONTRIBUTING.md as the standard 'bundle config
   local.opencode-ruby <path>' pattern, which is what Bundler ships
   for this use case.

3. Tighten opencode-ruby runtime dep from '~> 0.0.1.alpha1' to
   '= 0.0.1.alpha1' (Tobi T1: ~> during alpha is aspirational; pin
   exactly until the public API stabilizes).

Same commit also switches all forward-looking URLs (gemspec homepage,
metadata, README link to opencode-ruby) from Gitea to GitHub since the
gems will eventually publish there. Functional 'git:' URL in
ajent-rails' Gemfile stays on Gitea — that's where the gems actually
are right now; ajent-rails Gemfile flips to GitHub when the user does
the actual remote setup.

Test assertion in loading_test was tightened to match either an
installed-gem path ('gems/opencode-X-VERSION/') or a sibling-repo
checkout ('/opencode-X/'), via a small GEM_PATH_PATTERN helper.

15 tests, 50 assertions, 0 failures.

opencode-rails.gemspec

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "lib/opencode/rails/version"
+require_relative "lib/opencode/rails_version"
 
 Gem::Specification.new do |spec|
   spec.name          = "opencode-rails"
@@ -19,22 +19,25 @@ Gem::Specification.new do |spec|
     production-grade OpenCode streaming without rolling your own
     boilerplate.
   DESC
-  spec.homepage      = "https://gitea.krishnan.ca/ajaynomics/opencode-rails"
+  spec.homepage      = "https://github.com/ajaynomics/opencode-rails"
   spec.license       = "MIT"
   spec.required_ruby_version = ">= 3.2.0"
 
+  spec.metadata["homepage_uri"]    = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
-  spec.metadata["changelog_uri"]   = "#{spec.homepage}/src/branch/main/CHANGELOG.md"
+  spec.metadata["changelog_uri"]   = "#{spec.homepage}/blob/main/CHANGELOG.md"
   spec.metadata["bug_tracker_uri"] = "#{spec.homepage}/issues"
 
   spec.files = Dir.glob("lib/**/*.rb") +
+               Dir.glob("examples/**/*.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"
+  # this gem builds on. During alpha both gems evolve in lockstep — we pin
+  # exactly (= not ~>) so that consumers always pick the version this gem
+  # was tested against. Bump to alpha2 when the paired release ships.
+  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