fix: internal plugins are mistakenly recognized as external plugins

This fixes a problem where external plugin commands, such as
fusuma-sendkey, mistakenly recognize fusuma's internal plugins as
external plugins.

Author: iberianpig

lib/fusuma/plugin/manager.rb

@@ -40,6 +40,7 @@ def fusuma_external_plugin_paths
             plugin_gemspec = Gem::Specification.load(plugin_gemspec_path)
             fusuma_gemspec_path = File.expand_path("../../../fusuma.gemspec", __dir__)
             fusuma_gemspec = Gem::Specification.load(fusuma_gemspec_path)
+            next if plugin_gemspec == fusuma_gemspec
 
             if plugin_gemspec.dependencies.find { |d| d.name == "fusuma" }&.match?(fusuma_gemspec)
               siblings_plugin