feat(ci): use PROJECT_PAT for project board, populate board in dry-run

- Add PROJECT_PAT secret for project board GraphQL calls, falling
  back to GITHUB_TOKEN if not set
- Dry-run now populates the project board with decisions (confidence,
  reason, evidence fields) while still skipping labels/comments/closing
- Extract addToProjectWithFields helper to reduce duplication

.github/workflows/issue-resolution-triage.yml

@@ -28,6 +28,7 @@ jobs:
     runs-on: ubuntu-latest
     env:
       GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      PROJECT_PAT: ${{ secrets.PROJECT_PAT }}
       DRY_RUN: "true"
       MAX_ISSUES: "100"
       REPO: ${{ github.repository }}