Fixup transition model generator for namespaced models

[JoeSouthan]

Fixes #460, #546

Namespaced models were not having their transition class generated correctly

Also fixes issue where the model is created after the migration.

Output:

# 20250905103710_create_game_chess_transitions.rb
class CreateGameChessTransitions < ActiveRecord::Migration[8.0]
  def change
    create_table :game_chess_transitions do |t|
      t.string :from_state, null: false
      t.string :to_state, null: false
      t.jsonb :metadata, default: {}
      t.integer :sort_key, null: false
      t.integer :game_chess_id, null: false
      t.boolean :most_recent, null: false

      # If you decide not to include an updated timestamp column in your transition
      # table, you'll need to configure the `updated_timestamp_column` setting in your
      # migration class.
      t.timestamps null: false
    end

    # Foreign keys are optional, but highly recommended
    add_foreign_key :game_chess_transitions, :game_chesses

    add_index(:game_chess_transitions,
              %i[game_chess_id sort_key],
              unique: true,
              name: "index_game_chess_transitions_parent_sort")
    add_index(:game_chess_transitions,
              %i[game_chess_id most_recent],
              unique: true,
              where: "most_recent",
              name: "index_game_chess_transitions_parent_most_recent")
  end
end

[Tabby]

Looks good to me. There's potential for a little more refactoring of the templates, but nothing essential