[Mark Brown (markjbrown)]

Summary

• Replace media/application_architecture.png with a crisp, light-background diagram using Helvetica typography and restrained blue/purple accents, preserving the existing image path.
• Show the current architecture accurately: the command-line core discovers and composes extensions through MEF, source records stream asynchronously to the sink as IDataItem instances, and shared contracts keep the core independent of plug-in implementations.
• Include the editable media/application_architecture.excalidraw source and update the README image description and source link. No application code changes.

Verification

• Grounded the diagram in ExtensionLoader, RunCommand, source/sink interfaces, concrete extension exports, and the core project references.
• Exported with the Excalidraw renderer and visually inspected the full 1600 × 1574 PNG and its 422 × 415-pixel portfolio preview.
• Confirmed the source opens in Excalidraw with all 23 editable elements and bound source/sink labels intact; verified JSON references, PNG integrity, and git diff --check.
• The portfolio copy and editable source were stored locally before this PR; matching hashes, a successful Jekyll build, and browser rendering were confirmed.

[Mark Brown (markjbrown)]

Phil Nachreiner (@philnach) This documentation PR is ready to merge once the required approval is recorded. I rechecked head ce916950: all seven CI checks pass and there are no unresolved review discussions.

I inspected the rendered diagram and its editable source, verified the 23 elements and their bindings, checked the README image/source links, and confirmed the MEF loading and asynchronous IDataItem source-to-sink flow against the implementation. No additional changes were needed.