Generate cover metadata during developer guide build

[shai-almog]

Summary

• add a workflow step that duplicates the developer guide cover art and injects the build version and date into the SVG copy
• feed the generated cover into the Asciidoctor HTML/PDF builds and package it with the other artifacts
• make the guide reference the cover path via an attribute and ignore the generated SVG in git

Testing

• not run (not requested)

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https://chatgpt.com/codex/tasks/task_e_68f7a5b7a28483319ba36725052dc2bb

[github-actions]

Developer Guide build artifacts are available for download from this workflow run:

• Developer Guide HTML package
• Developer Guide PDF