The static-HTML pipeline differs from the rich pipeline only by a
context flag - both share the same filter chain. The dedicated
`Markdown::StaticHtmlFormatter` and `:markdown_as_static_html`
format symbol were pure boilerplate around that one-line override.
Callers now pass `format: :rich, static_html: true` and the matchers
read `context[:static_html]` directly.
Kabiru Mwenja
94c13c11fa