chore: enforce least-privilege permissions in GitHub Actions workflows

Set top-level `permissions: {}` on all workflows and move required
permissions to job level. Switch publish.yml from secrets.PAT to
secrets.GITHUB_TOKEN so semantic-release can comment on PRs/issues.

.github/workflows/publish.yml

@@ -6,7 +6,7 @@ on:
     branches:
       - main
 
-permissions: read-all
+permissions: {}
 
 env:
   NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
@@ -72,5 +72,5 @@ jobs:
       - name: Semantic Release
         uses: cycjimmy/semantic-release-action@b12c8f6015dc215fe37bc154d4ad456dd3833c90 # v6.0.0
         env:
-          GITHUB_TOKEN: ${{ secrets.PAT }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           NPM_TOKEN: ${{ secrets.NPM_TOKEN }}