Fix bug: fix error for Psych 4.0.0 or later

If the version of Psych was 4.0.0 or later, an error occurred
with hookcc.

Even a simple example like this will cause an error:

  $ ./outvoke.rb -e 'hookcc("every-sec") { e }'

This bug appeared in version 0.0.99.20241123 (1c328546).

Outvoke used Object#to_yaml and YAML.load for deep copying.
This commit makes the change to use YAML.unsafe_load instead of
YAML.load.

Since YAML.unsafe_load is executed immediately after executing
Object#to_yaml, the security risk is considered small. However,
please note that this has not been carefully verified to ensure
it is safe in all cases.

In Outvoke, the approach for deep copying may be radically
changed in the future.

outvoke.rb

 #!/usr/bin/env ruby
 #
 # ==========================================================================
-# Outvoke -- version 0.0.99.20241231
+# Outvoke -- version 0.0.99.20250614
 #
 # written by cleemy desu wayo / Licensed under CC0 1.0
 #
@@ -31,7 +31,7 @@ class Outvoke
 
     @version = Struct.new(:branch, :body).new(
       '0.1',
-      '0.0.99.20241231'
+      '0.0.99.20250614'
     )
 
     @ds               = Hash.new
@@ -270,7 +270,7 @@ class Outvoke
 
     return unless event.m
 
-    event.m = event.m.to_a   # with YAML.load and to_yaml in mind
+    event.m = event.m.to_a   # with YAML.unsafe_load and to_yaml in mind
 
     event.hookby = hook["hookby"]
 
@@ -358,7 +358,7 @@ module OutvokeDSL
     def register_hookcc(ds_cond, event_cond, hookby, &block)
       if block_given?
         $outvoke.register_proc(ds_cond, event_cond, hookby) do |e; tmp_event|
-          tmp_event = YAML.load(e.to_yaml)    # deep copy
+          tmp_event = YAML.unsafe_load(e.to_yaml)    # deep copy
 
           Thread.start do
             Thread.current["hookcc_result"] = instance_exec(tmp_event , &block)