refactor: replace repeated `echo` statements in CI workflows with heredoc syntax

## Summary

Several CI workflow and action files use repeated `echo` statements to print multiline output in `run:` blocks. These should be refactored to use [indented heredoc syntax (`<<-`)](https://linuxize.com/post/bash-heredoc/#indented-heredocs-with--) for better readability and maintainability.

## Motivation

Raised in PR #9846 (comment: https://github.com/Comfy-Org/ComfyUI_frontend/pull/9846#discussion_r2928785070) by @DrJKL.

**Before:**
```yaml
run: |
echo "::error::Linting/formatting issues found."
echo ""
echo "Please run these commands locally:"
echo " pnpm lint:fix"
echo " pnpm format"
```

**After (using indented heredoc):**
```yaml
run: |
cat <<-'EOF'
::error::Linting/formatting issues found.

Please run these commands locally:
pnpm lint:fix
pnpm format
EOF
```

## Files to Refactor

The following files have 3 or more `echo` statements and are candidates for this refactor (sorted by echo count):

| File | Echo count |
|------|-----------|
| `.github/workflows/pr-update-playwright-expectations.yaml` | 57 |
| `.github/workflows/release-biweekly-comfyui.yaml` | 55 |
| `.github/workflows/pr-backport.yaml` | 49 |
| `.github/workflows/release-branch-create.yaml` | 36 |
| `.github/workflows/ci-oss-assets-validation.yaml` | 26 |
| `.github/actions/comment-release-links/action.yaml` | 17 |
| `.github/workflows/ci-dist-telemetry-scan.yaml` | 17 |
| `.github/workflows/publish-desktop-ui.yaml` | 14 |
| `.github/workflows/release-version-bump.yaml` | 14 |
| `.github/workflows/ci-lint-format.yaml` | 13 |
| `.github/workflows/version-bump-desktop-ui.yaml` | 10 |
| `.github/workflows/api-update-manager-api-types.yaml` | 9 |
| `.github/workflows/api-update-registry-api-types.yaml` | 9 |
| `.github/workflows/cloud-backport-tag.yaml` | 9 |
| `.github/workflows/weekly-docs-check.yaml` | 7 |
| `.github/workflows/ci-tests-e2e-forks.yaml` | 5 |
| `.github/workflows/ci-tests-storybook-forks.yaml` | 5 |
| `.github/workflows/ci-tests-storybook.yaml` | 4 |
| `.github/workflows/release-npm-types.yaml` | 12 |
| `.github/actions/setup-comfyui-server/action.yaml` | 3 |
| `.github/workflows/publish-desktop-ui-on-merge.yaml` | 3 |
| `.github/workflows/release-draft-create.yaml` | 3 |

> Note: Not every `echo` needs replacing — single-line echoes or `echo "$VAR"` patterns are fine as-is. Focus on consecutive `echo` blocks used to print static multiline messages.

## References
- Heredoc docs: https://linuxize.com/post/bash-heredoc/#indented-heredocs-with--
- Raised in: https://github.com/Comfy-Org/ComfyUI_frontend/pull/9846#discussion_r2928785070

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-9864-refactor-replace-repeated-echo-statements-in-CI-workflows-with-heredoc-syntax-3226d73d36508179b52dc006f5e2803f) by [Unito](https://www.unito.io)