make rcm usable as a gem from any directory, fix bugs and tests

- Add lib/rcm.rb entry point and bin/rcm CLI executable
- Update gemspec: v0.1.0, proper files list, executables, runtime deps
- Support standalone arg parsing and --hosts filtering in options
- Fix inverted logic and typo in FileBackup#different? (== vs !=, cecksum_b)
- Fix unqualified File.directory? resolving to RCM::File in Directory
- Fix test_chown assertions running before evaluate! creates files
- Add setup to file tests to prevent order-dependent failures

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

2 files changed, 6 insertions, 2 deletions

diff --git a/lib/dslkeywords/file.rb b/lib/dslkeywords/file.rb
index aa1b725..9a44f72 100644
--- a/lib/dslkeywords/file.rb
+++ b/lib/dslkeywords/file.rb
@@ -23,7 +23,7 @@ module RCM
     def different?(file_a, file_b)
       checksum_a = Digest::SHA256.file(file_a).hexdigest
       checksum_b = Digest::SHA256.file(file_b).hexdigest
-      [checksum_a == checksum_b, checksum_a, cecksum_b]
+      [checksum_a != checksum_b, checksum_a, checksum_b]
     end
 
     private
@@ -320,7 +320,7 @@ module RCM
       end
 
       do? "Copying #{source_path} -> #{@file_path} resursively" do
-        if File.directory?(@file_path)
+        if ::File.directory?(@file_path)
           Dir["#{source_path}/*"].each { FileUtils.cp_r(_1, @file_path) }
         else
           FileUtils.cp_r(source_path, @file_path)
diff --git a/lib/dslkeywords/given.rb b/lib/dslkeywords/given.rb
index fa14e68..ba61703 100644
--- a/lib/dslkeywords/given.rb
+++ b/lib/dslkeywords/given.rb
@@ -17,6 +17,10 @@ module RCM
     def met?
       return false if @conds.key?(:hostname) && Socket.gethostname != @conds[:hostname].to_s
 
+      # When --hosts is specified, only run on the listed hosts
+      hosts = option(:hosts)
+      return false if hosts.any? && !hosts.include?(Socket.gethostname)
+
       true
     end
   end