feat(ack): bind test env to deployer and add regression mode

ACK 0.19.0 hands test-environment deploys to the deployer skill,
documents bug-fix as a first-class scenario, and adds
docs/ack/regression.yaml harvest plus a /ack regression run.

skills/ack/examples/tasks.example.yaml

@@ -3,13 +3,14 @@
 version: 1
 updatedAt: "2026-07-06T09:40:00+08:00"
 source: "Coordinator (PM) Agent"
-ackVersion: "0.18.0"
+ackVersion: "0.19.0"
 project:
   name: "notes-web"
   baseUrl: "http://localhost:5173"
   overlayFile: "docs/ack/project.md"
   knowledgeFile: "docs/ack/knowledge.yaml"
   deliveryFile: "docs/ack/delivery.yaml"
+  regressionFile: "docs/ack/regression.yaml"
   orchestration:
     profileVersion: 1
     mode: "manual"
@@ -96,6 +97,7 @@ project:
 
 workerReceipts: []
 deliveryRuns: []
+regressionRuns: []
 
 summary:
   verified: ["BUG-002"]