feat(workflows): add /change-risk slash command for PR risk assessment (#434)

Add an on-demand agentic workflow triggered by /change-risk on pull
requests. The agent analyses the diff for breaking API changes,
behavioral shifts, pipeline output changes, and dependency impact,
then submits a formal PR review (APPROVE or REQUEST_CHANGES).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jamesadevine

.github/aw/actions-lock.json

@@ -1,5 +1,10 @@
 {
   "entries": {
+    "actions/github-script@v8": {
+      "repo": "actions/github-script",
+      "version": "v8",
+      "sha": "ed597411d8f924073f98dfc5c65a23a2325f34cd"
+    },
     "actions/github-script@v9": {
       "repo": "actions/github-script",
       "version": "v9",
@@ -10,6 +15,11 @@
       "version": "v9.0.0",
       "sha": "d746ffe35508b1917358783b479e04febd2b8f71"
     },
+    "github/gh-aw-actions/setup@v0.62.0": {
+      "repo": "github/gh-aw-actions/setup",
+      "version": "v0.62.0",
+      "sha": "b2c35f34e1013dd9ed2a84c559e2b2fec9ad38e6"
+    },
     "github/gh-aw/actions/setup@v0.68.1": {
       "repo": "github/gh-aw/actions/setup",
       "version": "v0.68.1",