Add standalone Pandoc (pandoc-cli) to baseline optional packages

[geritwagner]

Motivation

• Provide a system-level pandoc installation managed by the existing baseline role so Pandoc is available independently of Quarto and is included in the unmanaged-package audit.

Description

• Add Fedora package pandoc-cli to baseline_optional_packages in roles/baseline/defaults/main.yml and keep the list alphabetized, without creating a new role or touching the quarto role.
• Update docs/baseline.qmd to note that the workstation supplies a system-level pandoc (via pandoc-cli) and add pandoc --version to the baseline verification check, while not adding pandoc-pdf and leaving baseline_managed_dnf_packages unchanged.

Testing

• Ran python -m unittest tests.test_baseline_role -v and all baseline role tests passed.
• Ran a validation script that confirmed baseline_optional_packages remains alphabetically ordered, pandoc-cli is present, and pandoc-pdf is absent.
• Ran git diff --check and basic repository checks; attempting the full pytest -q collection failed due to a missing environment dependency (ruamel.yaml) unrelated to these changes.

---

Codex Task