The misclassified-wisps check could detect issues that should be wisps
but couldn't fix them because bd update lacked an --ephemeral flag.
Now that beads supports `bd update <id> --ephemeral` (steveyegge/beads#1263),
implement the actual fix to mark detected issues as ephemeral.
Closes#852
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>