fix(rube): load erb at require time, not inside generate

test_generate_returns_an_object_not_bytes errored on roughly 1 run in 12
under Minitest's random ordering.

assert_kind_of ERB, chain.generate evaluates the ERB constant before calling
generate, and generate was performing a lazy require of erb inside itself. If
that test ran before anything else had loaded erb, the constant did not exist.

The lazy require was the defect rather than the test. A require buried in a
method makes constant availability depend on call order for every caller, not
just this one. Moved to the top of the file.

Verified across 40 randomized runs, 0 unstable. The previous commit shipped
this suite showing 1 error and should not have.

PROJECTS/beginner/deserialization-gadget-lab/lib/rube/chains/erb_def_method.rb

@@ -1,6 +1,8 @@
 # ©AngelaMos | 2026
 # erb_def_method.rb
 
+require "erb"
+
 module Rube
   module Chains
     class ErbDefMethod < Base
@@ -47,8 +49,6 @@ module Rube
       end
 
       def generate
-        require "erb"
-
         object = ERB.allocate
         object.instance_variable_set(IVAR_SRC, src)
         object.instance_variable_set(IVAR_FILENAME, DEFAULT_FILENAME)