Add unlock functionality for reopened issues and PRs in locker workflow (#119003)

This PR enhances the `.github/workflows/locker.yml` workflow to
automatically unlock issues and pull requests when they are reopened,
addressing the need to make previously locked items accessible again
when discussion resumes.

## Changes Made

### New Event Triggers
- Added `issues.reopened` trigger to detect when closed issues are
reopened
- Added `pull_request_target.reopened` trigger to detect when closed PRs
are reopened

### Enhanced Job Logic
- **Lock job** (renamed from `main` for clarity):
- Added condition to prevent execution on reopened events:
`github.event_name != 'issues' && github.event_name !=
'pull_request_target'`
- Preserves existing functionality for scheduled runs and manual
dispatch
  
- **New unlock job**:
- Only executes when issues or PRs are reopened: `github.event.action ==
'reopened'`
  - Uses `actions/github-script@v7` with GitHub REST API to unlock items
- Handles both issues and pull requests with a single step (since GitHub
treats PRs as issues in the API)
- Only unlocks if the item is actually locked:
`github.event.issue.locked == true`

### Workflow Behavior
- **Before**: Issues/PRs remained locked after being reopened,
preventing further discussion
- **After**: Issues/PRs are automatically unlocked when reopened,
allowing immediate participation

## Technical Implementation

The unlock functionality uses the GitHub Issues API (which also handles
PRs) through `actions/github-script@v7`:

```javascript
await github.rest.issues.unlock({
  issue_number: context.issue.number,
  owner: context.repo.owner,
  repo: context.repo.repo,
});
```

This ensures that when maintainers or contributors reopen issues or PRs
for continued discussion, they won't encounter locked conversation
threads that prevent community engagement.

Fixes the workflow gap where reopened items remained inaccessible for
comments despite being active again.

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---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: akoeplinger <[email protected]>
Co-authored-by: Alexander Köplinger <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: 3 people

.github/workflows/locker.yml

@@ -1,4 +1,4 @@
-name: Locker - Lock stale issues and PRs
+name: Locker - Lock stale issues and PRs, unlock reopened ones
 on:
   schedule:
     - cron: '37 8 * * *' # Once per day, early morning PT
@@ -13,14 +13,21 @@ on:
         required: true
         default: "30"
 
+  issues:
+    types: [reopened]
+
+  pull_request_target:
+    types: [reopened]
+
 permissions:
   issues: write
   pull-requests: write
 
 jobs:
-  main:
+  lock:
     runs-on: ubuntu-latest
-    if: ${{ github.repository_owner == 'dotnet' }}
+    # Only run the locking job for scheduled runs and manual dispatch, not for reopened events
+    if: ${{ github.repository_owner == 'dotnet' && (github.event_name == 'schedule' || github.event_name == 'workflow_dispatch') }}
     steps:
       - name: Checkout Actions
         uses: actions/checkout@v6
@@ -35,3 +42,20 @@ jobs:
         with:
           daysSinceClose:  ${{ fromJson(inputs.daysSinceClose  || 30) }}
           daysSinceUpdate: ${{ fromJson(inputs.daysSinceUpdate || 30) }}
+
+  unlock:
+    runs-on: ubuntu-latest
+    # Only run the unlocking job when issues or PRs are reopened
+    if: ${{ github.repository_owner == 'dotnet' && (github.event_name == 'issues' || github.event_name == 'pull_request_target') && github.event.action == 'reopened' }}
+    steps:
+      - name: Unlock if issue/PR is locked
+        uses: actions/github-script@v7
+        if: ${{ github.event.issue.locked == true }}
+        with:
+          script: |
+            console.log(`Unlocking locked issue/PR #${context.issue.number}.`);
+            await github.rest.issues.unlock({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+            });