fix: add RBS inline annotations for @min_word_length

Add missing instance variable declarations for Steep type checker:
- @min_word_length in Bayes, TFIDF, LogisticRegression, LSI
- @config and method signatures in Config module

These annotations allow the type checker to properly verify
the new min_word_length parameter added in this PR.

Author: cardmagic

lib/classifier/bayes.rb

@@ -20,6 +20,7 @@ class Bayes # rubocop:disable Metrics/ClassLength
     # @rbs @cached_vocab_size: Integer?
     # @rbs @dirty: bool
     # @rbs @storage: Storage::Base?
+    # @rbs @min_word_length: Integer
 
     attr_accessor :storage
 

lib/classifier/config.rb

@@ -1,22 +1,29 @@
 # rbs_inline: enabled
 
 module Classifier
+  # @rbs @config: Config?
+
   # This lazy initialization is not thread-safe.
   # In multi-threaded environments, ensure this method is called
   # or configuration is set explicitly during startup before using classifiers.
+  # @rbs () -> Config
   def config
     @config ||= Config.new
   end
 
+  # @rbs () { (Config) -> void } -> void
   def configure(&block)
-    block.call(config)
+    block&.call(config)
   end
 
   module_function :config, :configure
 
   class Config
+    # @rbs @min_word_length: Integer
+
     attr_accessor :min_word_length #: Integer
 
+    # @rbs () -> void
     def initialize
       @min_word_length = 3
     end

lib/classifier/logistic_regression.rb

@@ -34,6 +34,7 @@ class LogisticRegression # rubocop:disable Metrics/ClassLength
     # @rbs @fitted: bool
     # @rbs @dirty: bool
     # @rbs @storage: Storage::Base?
+    # @rbs @min_word_length: Integer
 
     attr_accessor :storage
 

lib/classifier/lsi.rb

@@ -80,6 +80,7 @@ class LSI
     # @rbs @u_matrix: Matrix?
     # @rbs @max_rank: Integer
     # @rbs @initial_vocab_size: Integer?
+    # @rbs @min_word_length: Integer
 
     attr_reader :word_list, :singular_values
     attr_accessor :auto_rebuild, :storage

lib/classifier/tfidf.rb

@@ -28,6 +28,7 @@ class TFIDF
     # @rbs @fitted: bool
     # @rbs @dirty: bool
     # @rbs @storage: Storage::Base?
+    # @rbs @min_word_length: Integer
 
     attr_reader :vocabulary, :idf, :num_documents
     attr_accessor :storage