Add missing actions: write permission to stale workflow

[Copilot]

This PR adds the missing actions: write permission to the stale workflow job that uses actions/stale.

Background

The actions/stale action requires the actions: write permission to delete its old cache before saving a new one. Without this permission, the action may not function correctly.

Changes

Updated .github/workflows/stale.yml to include actions: write in the permissions block for the stale job:

permissions:
  actions: write  # because actions/stale deletes its old cache before saving new one
  issues: write  # for actions/stale to close stale issues
  pull-requests: write  # for actions/stale to close stale PRs

The permission is placed in the correct order (after contents: read and before issues: write and pull-requests: write) and follows the existing comment style for consistency.

Fixes #[issue_number]

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add missing actions/stale permission</issue_title>
<issue_description>Check if any workflow jobs are using actions/stale.

If so, make sure that the permissions block for that job contains

actions: write

If any of the other permissions lines have trailing comments, then add a trailing comment for this one too:

actions: write # because actions/stale deletes its old cache before saving new one

Place this new permission in a specific order within the permissions, directly before both:

issues: write
pull-requests: write

(which implicitly means after contents: read)</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #85

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