docs(diagrams): re-export PNGs to match the corrected sources

Renders diagrams 1, 3, 4, 5 and 6 from their .excalidraw sources so the images
carry the corrected blast-radius semantics and the re-captured benchmark
numbers, instead of the figures they were exported with before.

Exported headlessly through the real @excalidraw/excalidraw exportToBlob at 2x,
so the hand-drawn strokes and Excalifont match a GUI export. Doing it from the
source files avoids the failure mode that produced the previous three attempts:
excalidraw.com restores the last canvas from local storage, so exporting after
reopening re-renders the cached scene rather than the file on disk — and saving
then writes that stale scene back over the corrected file.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JNv8JqBb46stATZYUinQtn