feat(lifecycle): implement DispatcherJob

Replace no-op stub with full perform body: find delivery by id, skip if
blank, delegate to Captain::Lifecycle::Dispatcher#call. Add retry_on
with polynomially_longer backoff (3 attempts). Spec covers dispatcher
delegation and graceful skip for missing records.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

enterprise/app/jobs/captain/lifecycle/dispatcher_job.rb

@@ -2,12 +2,16 @@
 
 class Captain::Lifecycle::DispatcherJob < ApplicationJob
   queue_as :default
+  retry_on StandardError, wait: :polynomially_longer, attempts: 3
 
   def self.perform_at(fire_at, delivery_id)
     set(wait_until: fire_at).perform_later(delivery_id)
   end
 
   def perform(delivery_id)
-    # Stub — full implementation lands in Task 16.
+    delivery = Captain::Lifecycle::Delivery.find_by(id: delivery_id)
+    return if delivery.blank?
+
+    Captain::Lifecycle::Dispatcher.new(delivery).call
   end
 end

spec/enterprise/jobs/captain/lifecycle/dispatcher_job_spec.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Captain::Lifecycle::DispatcherJob do
+  let(:delivery) { create(:captain_lifecycle_delivery) }
+
+  it 'calls Dispatcher#call' do
+    dispatcher = instance_double(Captain::Lifecycle::Dispatcher)
+    expect(Captain::Lifecycle::Dispatcher)
+      .to receive(:new)
+      .with(instance_of(Captain::Lifecycle::Delivery))
+      .and_return(dispatcher)
+    expect(dispatcher).to receive(:call)
+
+    described_class.perform_now(delivery.id)
+  end
+
+  it 'silently skips missing delivery records' do
+    expect { described_class.perform_now(-1) }.not_to raise_error
+  end
+end