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>

1 files changed, 18 insertions, 0 deletions

diff --git a/bin/rcm b/bin/rcm
new file mode 100755
index 0000000..2a7b6cd
--- /dev/null
+++ b/bin/rcm
@@ -0,0 +1,18 @@
+#!/usr/bin/env ruby
+# CLI entry point for RCM configuration management.
+# Usage: rcm <config.rb> [--dry] [--debug] [--hosts host1,host2]
+
+if ARGV.empty? || ARGV.first.start_with?('-')
+  warn "Usage: rcm <config.rb> [--dry] [--debug] [--hosts host1,host2]"
+  exit 1
+end
+
+config_file = ARGV.shift
+
+unless File.exist?(config_file)
+  warn "Error: file not found: #{config_file}"
+  exit 1
+end
+
+require 'rcm'
+load config_file