CI: skip draft-pr-policy checkout on issue-only comments (#6519)

* ci: skip draft-pr-policy checkout on issue-only comments

The issue_comment event fires for comments on both issues and PRs;
draft-pr-policy only cares about PR draft-staleness, so short-circuit
before checkout when the comment is on a plain issue. Also switch all
three jobs to a sparse, shallow checkout since they only need
.github/scripts to load the github-script payload.

* ci: also skip draft-pr-policy on bot-authored PR comments

draft-pr-policy.js already excludes Bot comments when deciding whether
a draft was revived, so a bot comment (e.g. review-checklist posting
its checklist) can never do anything meaningful here — it still ran
checkout + API calls only to no-op. Filter it out at the same if:
using the free github.event.comment.user.type field.

* ci: skip checkout for draft-pr-policy on non-draft PR comments

Even after filtering out issue-only and bot comments, a human comment
on any non-draft PR still paid for a full checkout just to have the
script itself discover pr.draft is false and return. Add a cheap
pulls.get-only pre-check step (no checkout required) and gate the real
checkout + script load on its result.

.github/workflows/stale-pr-policy.yml

@@ -30,6 +30,8 @@ jobs:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           persist-credentials: false
+          sparse-checkout: .github/scripts
+          fetch-depth: 1
       - uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
         with:
           script: |
@@ -37,17 +39,39 @@ jobs:
             await runMarkStale({ github, context, core });
 
   draft-pr-policy:
-    if: github.repository_owner == 'HDFGroup'
+    if: >-
+      github.repository_owner == 'HDFGroup' &&
+      (github.event_name != 'issue_comment' ||
+       (github.event.issue.pull_request != null && github.event.comment.user.type != 'Bot'))
     runs-on: ubuntu-latest
     permissions:
       contents: read
       issues: write
       pull-requests: write
     steps:
+      # No checkout needed here — just an API call to see if this comment's
+      # PR is even a draft, before paying for checkout + loading the script.
+      - name: Check draft status
+        id: check
+        if: github.event_name == 'issue_comment'
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        with:
+          script: |
+            const { data: pr } = await github.rest.pulls.get({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.payload.issue.number,
+            });
+            core.setOutput('is_draft', pr.draft ? 'true' : 'false');
+
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        if: steps.check.outputs.is_draft != 'false'
         with:
           persist-credentials: false
+          sparse-checkout: .github/scripts
+          fetch-depth: 1
       - uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        if: steps.check.outputs.is_draft != 'false'
         with:
           script: |
             const { runDraftPolicy } = require('${{ github.workspace }}/.github/scripts/draft-pr-policy.js');
@@ -65,6 +89,8 @@ jobs:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           persist-credentials: false
+          sparse-checkout: .github/scripts
+          fetch-depth: 1
       - uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
         with:
           script: |