Shows pending_cek, reuse_stack count, and frames count in the error.
Also transfers reuse_stack from _active_vm at VmSuspended catch sites.
Finding: the Not callable: nil happens during cek_resume (pending_cek=false,
kont=12 frames). The CEK continuation tries to call a letrec function that
is nil because letrec bindings are in VM local SLOTS, not in the CEK env.
The VM→CEK boundary crossing during suspension loses the local slot values.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
giles
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