Add state github bot (#812)

<!-- CURSOR_SUMMARY -->
> [!NOTE]
> **Low Risk**
> Low risk GitHub Actions-only change that affects PR triage by
automatically labeling and closing inactive PRs; no runtime code paths
are modified.
> 
> **Overview**
> Adds a new GitHub Actions workflow (`.github/workflows/stale.yml`) to
automatically mark pull requests as `stale` after 14 days of inactivity
and close them after an additional 14 days.
> 
> The workflow runs daily (and can be manually triggered), exempts PRs
labeled `pinned` or `security`, and explicitly disables
staleness/closure for issues.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
cdac08e3f3a40ccee7a8f79f4962adcdbb2e79c0. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

.github/workflows/stale.yml

@@ -0,0 +1,31 @@
+name: Stale
+
+on:
+  schedule:
+    - cron: "0 0 * * *"
+  workflow_dispatch:
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+
+    steps:
+      - uses: actions/stale@v9
+        with:
+          start-date: "2026-04-07"
+          days-before-stale: 14
+          days-before-close: 14
+          stale-pr-message: >
+            This pull request has been automatically marked as stale because it has had no
+            activity for 14 days. It will be closed in 14 days if no further activity occurs.
+            If this is still relevant, please leave a comment or remove the stale label.
+          close-pr-message: >
+            This pull request has been closed due to inactivity. Feel free to reopen it if
+            it is still relevant.
+          stale-pr-label: stale
+          exempt-pr-labels: "pinned,security"
+          days-before-issue-stale: -1
+          days-before-issue-close: -1