UAPF-specification v2.1.0 makes cornerstone diagram interchange mandatory
(SEM-011). This file was hand-authored as logic only, with no
<bpmndi:BPMNDiagram>, so it could not render in any OMG modeler/viewer.
Adds the bpmndi/dc/di namespace declarations and a complete BPMNDiagram
with authored shapes (10) and edges (9) — a deterministic linear layout.
The <bpmn:process> logic is byte-identical; only DI was added.
UAPF-specification v2.0.0 mandates OMG-standard cornerstone extensions.
Renamed cornerstone files and updated references in README / docs /
processgit.mcp.yaml. Content of the BPMN/DMN files is unchanged.
