Revert "🐛 fix: checkout PR head SHA for issue_comment triggered workflows (llm-d#832)"

This reverts commit e69a146.

Author: zdtsw

.github/workflows/ci-pr-checks.yaml

@@ -52,7 +52,6 @@ jobs:
       pull-requests: read  # For reading PR details when triggered via issue_comment
     outputs:
       has_code_changes: ${{ steps.set-output.outputs.has_code_changes }}
-      pr_head_sha: ${{ steps.pr-info.outputs.pr_head_sha }}
     steps:
       - name: Get PR number for issue_comment events
         id: pr-info
@@ -109,10 +108,7 @@ jobs:
             echo "has_code_changes=true" >> $GITHUB_OUTPUT
           fi
 
-  # lint-and-test already runs on pull_request events; skip for issue_comment
-  # to avoid untrusted commenters triggering execution of PR code
   lint-and-test:
-    if: github.event_name != 'issue_comment'
     runs-on: ubuntu-latest
     steps:
       - name: Checkout source
@@ -254,32 +250,13 @@ jobs:
   e2e-tests:
     runs-on: ubuntu-latest
     needs: [lint-and-test, check-code-changes, check-full-tests]
-    if: >-
-      always() && (
-        (github.event_name == 'issue_comment' && needs.check-full-tests.outputs.run_full == 'true' && needs.check-code-changes.result == 'success') ||
-        (github.event_name == 'workflow_dispatch' && (
-          needs.check-full-tests.outputs.run_full == 'true' ||
-          (needs.check-code-changes.result == 'success' && needs.check-code-changes.outputs.has_code_changes == 'true')
-        )) ||
-        (github.event_name == 'pull_request' && needs.check-code-changes.result == 'success' && needs.check-code-changes.outputs.has_code_changes == 'true')
-      )
+    if: always() && (needs.check-full-tests.outputs.run_full == 'true' || (needs.check-code-changes.result == 'success' && needs.check-code-changes.outputs.has_code_changes == 'true'))
     timeout-minutes: 60
     permissions:
       contents: read
     steps:
-      - name: Validate PR head SHA for issue_comment events
-        if: github.event_name == 'issue_comment'
-        run: |
-          if [ -z "${{ needs.check-code-changes.outputs.pr_head_sha }}" ]; then
-            echo "::error::pr_head_sha is empty — refusing to fall back to main"
-            exit 1
-          fi
-          echo "Checkout will use PR head SHA: ${{ needs.check-code-changes.outputs.pr_head_sha }}"
-
       - name: Checkout source
         uses: actions/checkout@v4
-        with:
-          ref: ${{ needs.check-code-changes.outputs.pr_head_sha || '' }}
 
       - name: Extract Go version from go.mod
         run: sed -En 's/^go (.*)$/GO_VERSION=\1/p' go.mod >> $GITHUB_ENV