docs(hooks): document action hooks + hooks-action example

Adds a new 'Action hooks' section to docs-v2/docs/lifecycle-hooks.md
describing the action: union member, how it relates to customActions,
which deployers support it (kubectl, helm, kpt), and that it shares a
runtime with skaffold exec (so a single action definition is runnable
standalone or wrapped as a deploy hook).

Ships a runnable examples/hooks-action/ fixture (mirrored under
integration/examples/) with pre-deploy-check + post-deploy-smoke
actions and a minimal busybox Pod manifest so maintainers can smoke
test the new schema end-to-end.

Author: bogdannazarenko

docs-v2/content/en/docs/lifecycle-hooks.md

@@ -154,3 +154,42 @@ deploy:
             podName: hooks-example-deployment*
 ```
 This config snippet defines a simple `echo` command to run inside the containers that match `podName` and `containerName`, before and after each `kubectl` deploy. The `after` container commands are only run after the [deployment status checks]({{< relref "/docs/status-check" >}}) on the deployment are complete. Also, unlike the `sync` container hooks, skaffold cannot determine the target container from just the config definition, and needs the `podName` and `containerName`.
+
+## Action hooks
+
+Action hooks dispatch an existing [custom action]({{< relref "/docs/custom-actions" >}}) as a deploy hook. They are the recommended way to package containerized deploy steps — schema migrations, smoke tests, out-of-band integrations — because they reuse the same runtime as `skaffold exec`, meaning a single action definition is runnable standalone or as part of a deploy and inherits the action's `executionMode`, `runArgs`, and deploy-parameter env injection.
+
+### `before-deploy` and `after-deploy`
+
+Example: _skaffold.yaml_ snippet
+```yaml
+customActions:
+  - name: db-migrate
+    containers:
+      - name: migrator
+        image: myorg/migrator:latest
+        command: ["migrate", "up"]
+
+deploy:
+  kubectl:
+    manifests:
+      - deployment.yaml
+    hooks:
+      before:
+        - action:
+            name: db-migrate
+      after:
+        - action:
+            name: smoke-test
+customActions:
+  - name: smoke-test
+    containers:
+      - name: curl
+        image: curlimages/curl
+        command: ["curl", "-fsS", "http://my-service/healthz"]
+```
+
+The referenced action must exist under `customActions`; unknown names are rejected at config-load time. Action hooks honour the declared `failFast` semantics of the action itself: a non-zero container exit aborts the hook, and the wrapping deploy is reported as failed.
+
+Action hooks are currently supported on the kubectl, helm, and kpt deployers. The Cloud Run deployer retains its `host`-only hooks.
+

examples/hooks-action/README.md

@@ -0,0 +1,19 @@
+# hooks-action
+
+Demonstrates `deploy.hooks.before` / `after` referencing an existing
+custom action via the new `action:` hook form. Running:
+
+```
+skaffold deploy --default-repo=gcr.io/my-project
+```
+
+executes, in order:
+
+1. `pre-deploy-check` custom action (runs in a busybox container)
+2. the kubectl deploy itself
+3. `post-deploy-smoke` custom action
+
+Each referenced action must be declared under `customActions`; unknown
+names are rejected at config-load time. Action hooks reuse the same
+runtime as `skaffold exec`, so `skaffold exec pre-deploy-check` alone
+runs the hook standalone.

examples/hooks-action/k8s/deployment.yaml

@@ -0,0 +1,9 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: hooks-action-demo
+spec:
+  containers:
+    - name: app
+      image: busybox
+      command: ["sh", "-c", "while true; do echo hello; sleep 10; done"]

examples/hooks-action/skaffold.yaml

@@ -0,0 +1,33 @@
+apiVersion: skaffold/v4beta14
+kind: Config
+metadata:
+  name: hooks-action-demo
+
+customActions:
+  - name: pre-deploy-check
+    containers:
+      - name: check
+        image: busybox
+        command: ["sh", "-c"]
+        args: ["echo 'pre-deploy check ok'"]
+
+  - name: post-deploy-smoke
+    containers:
+      - name: smoke
+        image: busybox
+        command: ["sh", "-c"]
+        args: ["echo 'post-deploy smoke test ok'"]
+
+manifests:
+  rawYaml:
+    - k8s/deployment.yaml
+
+deploy:
+  kubectl:
+    hooks:
+      before:
+        - action:
+            name: pre-deploy-check
+      after:
+        - action:
+            name: post-deploy-smoke

integration/examples/hooks-action/k8s/deployment.yaml

@@ -0,0 +1,9 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: hooks-action-demo
+spec:
+  containers:
+    - name: app
+      image: busybox
+      command: ["sh", "-c", "while true; do echo hello; sleep 10; done"]

integration/examples/hooks-action/skaffold.yaml

@@ -0,0 +1,33 @@
+apiVersion: skaffold/v4beta14
+kind: Config
+metadata:
+  name: hooks-action-demo
+
+customActions:
+  - name: pre-deploy-check
+    containers:
+      - name: check
+        image: busybox
+        command: ["sh", "-c"]
+        args: ["echo 'pre-deploy check ok'"]
+
+  - name: post-deploy-smoke
+    containers:
+      - name: smoke
+        image: busybox
+        command: ["sh", "-c"]
+        args: ["echo 'post-deploy smoke test ok'"]
+
+manifests:
+  rawYaml:
+    - k8s/deployment.yaml
+
+deploy:
+  kubectl:
+    hooks:
+      before:
+        - action:
+            name: pre-deploy-check
+      after:
+        - action:
+            name: post-deploy-smoke