Eagerly execute column config blocks instead of forcing render

Change `renders_many :columns` to a lambda slot that executes the
configuration block at creation time. This eliminates the fragile
`header.column.to_s # force rendering` pattern in the template,
which relied on rendering a component purely for side effects.

The Column#call method is also removed since Column is no longer
rendered as a component — it serves as a configuration holder.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: myabc

app/components/primer/open_project/data_table.html.erb

@@ -7,7 +7,6 @@
         <% table.with_head(classes: "TableHead") do |thead| %>
           <% thead.with_row(classes: "TableRow") do |tr| %>
             <% headers.each do |header| %>
-              <% header.column.to_s # force rendering %>
               <% if header.sortable? %>
                 <%
                   tr.with_header(

app/components/primer/open_project/data_table.rb

@@ -42,7 +42,11 @@ class DataTable < Primer::Component
         Primer::BaseComponent.new(**system_arguments)
       }
 
-      renders_many :columns, Column
+      renders_many :columns, ->(**args, &block) {
+        column = Column.new(**args)
+        block&.call(column)
+        column
+      }
 
       # @param data [Array, ActiveRecord::Relation]
       #   A collection of rows that will be rendered inside the table

app/components/primer/open_project/data_table/column.rb

@@ -68,10 +68,6 @@ def header?
           @header.present? || super
         end
 
-        def call
-          content
-        end
-
         def render_cell(row)
           return @cell_block.call(row) if @cell_block
           return unless field