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/templates/regression.template.yaml

@@ -0,0 +1,7 @@
+# 复制为 docs/ack/regression.yaml。只有 Coordinator 写入；Test 通过回报提名。
+# 结构见 templates/regression.schema.json。
+version: 1
+updatedAt: "<YYYY-MM-DDTHH:mm:ss+TZ>"
+project:
+  name: "<project_name>"
+cases: []