migrate all diagrams to mermaid

[psifertex]

semantic-flags-diagram
workflow-concepts-diagram
BNIL-overview
context-aware-apis.png‎
efp-dialog-diagram

all contain hard-coded diagram layouts that would be better served if they can be migrated to mermaid for both searchability, themeability, and maintainability.

[psifertex]

One issue to note -- current zensical implementation doesn't mirror mermaid for offline, conflicting with the privacy, need to make sure that's resolved since we don't want to ship diagrams that don't work offline.