mama_word_switch_mark_work()'s stack-underflow guard checked dsp < 2,
requiring 3+ items, when it only ever needs the 2 IDX>NAME leaves it
(caddr u). Since dsp is index-based (2 items == dsp 1), this rejected
every normal call. MSG-SEND tail-calls SWITCH-MARK-WORK unconditionally,
so this fired on every message sent anywhere in the system -- visible
only where a caller happened to check the target VM's error flag
afterward (mama_word_vm_exec()'s "VM-EXEC: ERROR in Artemis" report).
Verified clean on all 3 architectures: boot reaches Startup: Artemis
live -> zuse@Hera] ok> with no VM-EXEC: ERROR line at all.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BWpNjdwPtFLuVLaAq44L9K
