vector copy crash in native runtime

[ceedubs]

Describe and demonstrate the bug

vector-copy!: not enough room in target vector

See the Discord discussion.

The following exception occurred:

vector-copy!: not enough room in target vector
  target length: 32
  needed length: 48
  context...:
   .../unison/vector-trie.rkt:708:8: insert-subtries
   .../unison/vector-trie.rkt:634:0: vector-trie-append
   .../private/arrow-val-first.rkt:486:18
   .../match/compiler.rkt:559:40: f704
   .../private/arrow-val-first.rkt:486:18
   .../unison/boot.ss:231:9: ref-02eqc1a8oc2mp5tgdmnc9hb1ihc0v1ks0eqkq4stus4mhktaa767s:impl
   .../unison/boot.ss:231:9: ref-020vpdghvn1r949il298taslo6fafbnvq5563afa84dtb5rvl9ge6:impl
   .../unison/boot.ss:231:9: ref-00ptaar2vu9ij80480uocvhrbmgtaovqju8jf9v5ng740t4r7n70i:impl
   .../unison/boot.ss:231:9: ref-02ssab25a05c19r48c0r903i9gle8m6n8stp32idoj5ma2jhncepk:impl
   .../racket/control.rkt:137:30
   .../unison/boot.ss:231:9: ref-03adfvjhvr4e1c6apo14jj13mg9dqmtknpns6fen85i6j8616drrg:impl
   .../unison/boot.ss:231:9: ref-01hfo09kp18o2hnm8cht2e7jah6s42348rltbt7a84hqac0ecmisq:impl
   .../racket/control.rkt:137:30
   [repeats 3 more times]
   .../unison/boot.ss:231:9: ref-011j1l98di0ckktui8gfjcgc2ldhqfso9033on18aptfbvog93qbc:impl
   .../racket/control.rkt:137:30
   ...

@dolio said that this looks like a bug in the guts of the list implementation.