ci: match both h2 and h3 area headings in auto-labeler (#36572)

GitHub issue forms render the "Area (Required)" field label at
inconsistent heading levels — some issues get `### Area` (h3), others
get `## Area` (h2). The `auto-label-by-package` workflow's regex was
hardcoded to `### Area`, silently skipping issues with `## Area`
headings and never applying package labels (e.g.
[#2471](https://github.com/langchain-ai/deepagents/issues/2471)).

.github/workflows/auto-label-by-package.yml

@@ -20,9 +20,15 @@ jobs:
           script: |
             const body = context.payload.issue.body || "";
 
-            // Extract text under "### Package" (handles " (Required)" suffix and being last section)
-            const match = body.match(/### Package[^\n]*\n([\s\S]*?)(?:\n###|$)/i);
-            if (!match) return;
+            // Extract text under "## Package" or "### Package" (handles " (Required)" suffix and being last section)
+            const match = body.match(/#{2,3} Package[^\n]*\n([\s\S]*?)(?:\n#{2,3} |$)/i);
+            if (!match) {
+              core.setFailed(
+                `Could not find "## Package" section in issue #${context.issue.number} body. ` +
+                `The issue template may have changed — update the regex in this workflow.`
+              );
+              return;
+            }
 
             const packageSection = match[1].trim();