rfd-processor: Bump ruby and npm dependencies

[notpeter]

• Follow-up to: rfd-processor: Add PDF test; pin ruby/js dependencies explicitly #476
• Bump asciidoctor from 2.0.20 (2023-05-18) to 2.0.26 (2025-10-24) changelog
• Bump asciidoctor-pdf from 2.3.2 (2022-09-17) to 2.3.24 (2025-11-15) changelog
• Bump rouge from 4.5.1 (2024-11-12) to 5.0.0 (2026-05-26) changelog
• Bump @mermaid-js/mermaid-cli from 11.4.0 (2024-11-04) to 11.16.0 (2026-06-29) changelog
• Leave oxidecomputer/asciidoctor-mermaid pinned to 0.4.1 (2022-09-19)
  • Consider asciidoctor-diagram as replacement in the future.

[notpeter]

Deployment plan:

1. Verify (as rfd user):

asciidoctor --version |grep -v Runtime
asciidoctor-pdf --version | grep -v Runtime
mmdc --version

gem list | grep -P '(asciidoctor|rouge|logger|base64)'
npm list -g | grep mermaid-js

2. Install updated dependencies

sudo gem install asciidoctor -v 2.0.26
sudo gem install asciidoctor-pdf -v 2.3.24
sudo gem install asciidoctor-mermaid -v 0.4.1
sudo gem install rouge -v 5.0.0
sudo gem install logger -v 1.7.0
sudo gem install base64 -v 0.3.0

sudo npm install -g @mermaid-js/mermaid-cli@11.16.0
sudo -u rfd env HOME=/home/rfd \
    "$(npm root -g)/@mermaid-js/mermaid-cli/node_modules/.bin/puppeteer" \
    browsers install chrome-headless-shell

3. Repeat step 1 (Verify)
4. Push a grammar/spelling fix commit to an RFD and verify PDF is generated correctly.