[actions] fix weekly action to "work" (#1214)

This pull request updates the
`.github/workflows/weekly-stable-updates.yml` file to enhance the
workflow for creating weekly stable updates issues. The changes
improve issue management by preventing duplicate issues, adding
permissions, and assigning issues to the appropriate assignee.

### Workflow Enhancements:

* Added `permissions` block to allow writing to issues.
* Updated the `schedule` trigger formatting for clarity.

### Issue Management Improvements:

* Introduced a check to prevent duplicate issues by searching for
  existing issues with the same title before creating a new one.
* Added a step to assign the newly created issue to the `@copilot`
  user using the `gh` CLI.
* Added `id: create-issue` to the "Create weekly stable updates issue"
  job for referencing outputs in subsequent steps.

Author: jonathanpeppers

.github/workflows/weekly-stable-updates.yml

@@ -1,9 +1,12 @@
 name: "Weekly Stable Updates"
 
+permissions:
+  issues: write
+
 on:
-  #schedule:
+  schedule:
     # Run every Monday at 9:00 AM UTC
-  #  - cron: '0 9 * * 1'
+    - cron: '0 9 * * 1'
   workflow_dispatch: # Allow manual triggering for testing
 
 jobs:
@@ -16,6 +19,7 @@ jobs:
       run: echo "date=$(date +'%Y%m%d')" >> $GITHUB_OUTPUT
 
     - name: Create weekly stable updates issue
+      id: create-issue
       uses: actions/github-script@v7
       with:
         github-token: ${{ secrets.GITHUB_TOKEN }}
@@ -39,12 +43,31 @@ jobs:
 
           And put the contents from this command in the PR description and commit messages.`;
 
+          // Check for existing issues with the same title
+          const existingIssues = await github.rest.issues.listForRepo({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            state: 'open',
+            per_page: 100
+          });
+          const duplicateIssue = existingIssues.data.find(issue => /^Stable Updates \d{8}$/.test(issue.title));
+          if (duplicateIssue) {
+            console.log(`Issue with title "${duplicateIssue.title}" already exists: #${duplicateIssue.number}`);
+            return;
+          }
+
           const response = await github.rest.issues.create({
             owner: context.repo.owner,
             repo: context.repo.repo,
             title: title,
             body: body,
-            assignees: ['copilot-swe-agent']
           });
           
           console.log(`Created issue #${response.data.number}: ${response.data.title}`);
+          core.setOutput('issue-number', response.data.number);
+
+    - name: Add assignee to issue
+      if: steps.create-issue.outputs.issue-number && steps.create-issue.outputs.issue-number != ''
+      run: gh issue edit ${{ steps.create-issue.outputs.issue-number }} --add-assignee "@copilot" -R dotnet/android-libraries
+      env:
+        GH_TOKEN: ${{ secrets.ANDROID_TEAM_PAT }}