Runtime gains hs-get-selection: prefers window.__test_selection stash,
falls back to real getSelection().toString(). Compiler rewrites
`(ref "selection")` to `(hs-get-selection)`. Generator detects the
createRange + setStart/setEnd + addRange block and emits a single
host-set! on __test_selection with the text slice; sidesteps the need
for a fully propagating DOM range/text-node mock.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
giles
d862efe811