ci: declare workflow-level contents: read on 4 workflows

Pins the default GITHUB_TOKEN to contents: read on the workflows in
.github/workflows/ that don't call a GitHub API beyond the initial
checkout. The other workflows in this directory are left implicit
because they need write scopes that a maintainer is better placed
to declare.

Motivation: CVE-2025-30066 (March 2025 tj-actions/changed-files
compromise) exfiltrated GITHUB_TOKEN from workflow logs. Per-workflow
caps bound runtime authority irrespective of repo or org default,
give drift protection if the default ever widens, and are credited
per-file by the OpenSSF Scorecard Token-Permissions check.

YAML validated locally with yaml.safe_load.

Signed-off-by: Arpit Jain <arpitjain099@gmail.com>

Author: arpitjain099

.github/workflows/build-tutorials-nightly.yml

@@ -27,6 +27,9 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}-${{ github.event_name == 'workflow_dispatch' }}-${{ github.event_name == 'schedule' }}
   cancel-in-progress: true
 
+permissions:
+  contents: read
+
 jobs:
   build:
     uses: ./.github/workflows/_build-tutorials-base.yml

.github/workflows/build-tutorials.yml

@@ -10,6 +10,9 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}-${{ github.event_name == 'workflow_dispatch' }}-${{ github.event_name == 'schedule' }}
   cancel-in-progress: true
 
+permissions:
+  contents: read
+
 jobs:
   build:
     uses: ./.github/workflows/_build-tutorials-base.yml

.github/workflows/check-redirects.yml

@@ -7,6 +7,9 @@ on:
      - '*/**/*.py'
      - '*/**/*.md'
 
+permissions:
+  contents: read
+
 jobs:
   check-redirects:
     runs-on: ubuntu-latest

.github/workflows/lintrunner.yml

@@ -10,6 +10,9 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}-${{ github.event_name == 'workflow_dispatch' }}
   cancel-in-progress: true
 
+permissions:
+  contents: read
+
 jobs:
   lintrunner:
     name: lintrunner