`&a [1, *a]` puts the self-reference after a plain value, so a guard that
only inspected the head of a sequence would miss it. Already caught; this
records that it is.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ND46Ci64DC3tzBy9aG81Nc
Signed-off-by: cliffhall <cliff@futurescale.com>