ci: add error handling to release-PR assign script (LAB-899)

Kody review on #61: JSON.parse + addAssignees threw unhandled on
malformed PR_JSON or API failure, failing the step with a raw stack
trace and no context. Wrap in try/catch and core.setFailed with the
repo, PR_JSON length (parse vs truncation diagnosis without dumping
the multi-KB PR body into logs), and error message. Still fails the
step — assignment failures must stay visible, not warn-and-pass.

Co-authored-by: multica-agent <github@multica.ai>

Author: 27Bslash6

.github/workflows/release.yml

@@ -53,13 +53,18 @@ jobs:
         with:
           github-token: ${{ steps.app-token.outputs.token }}
           script: |
-            const pr = JSON.parse(process.env.PR_JSON);
-            await github.rest.issues.addAssignees({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              issue_number: pr.number,
-              assignees: ['27Bslash6'],
-            });
+            try {
+              const pr = JSON.parse(process.env.PR_JSON);
+              await github.rest.issues.addAssignees({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: pr.number,
+                assignees: ['27Bslash6'],
+              });
+              core.info(`Assigned 27Bslash6 to release PR #${pr.number}`);
+            } catch (error) {
+              core.setFailed(`Failed to assign release PR in ${context.repo.owner}/${context.repo.repo} (PR_JSON length ${process.env.PR_JSON.length}): ${error.message}`);
+            }
 
   publish:
     needs: release-please