The metadata strategy returned None for images whose embedded workflow has
no positive PromptManager node, so the handler popped the batch FIFO for
them and every later batch image linked to the wrong prompt. It now returns
a tri-state: linked (prompt found), foreign (no PromptManager prompt in the
workflow, so the image is skipped and no fallback applies) or unknown (only
then the queue, snapshot, tracker and recent-prompt fallbacks run).