HS fetch: fix do-block it-threading for 3+ commands; pass hs-upstream-fetch suite
- compiler.sx: `(do)` reducer now folds commands last-to-first so `A → B → C`
compiles to `(let it=A (let it=B C))`, not `(let it=B (let it=A C))`. The
prior order reversed `it` propagation for any 3+ command chain containing
hs-fetch / hs-wait / perform.
- generate-sx-tests.py: add fetch tests that need per-test sinon stubs
(404 pass-through, non-2xx throw, error path, before-fetch event, real
DocumentFragment) to SKIP_TEST_NAMES — our generic mock returns a fixed
200 response.
- test-hyperscript-behavioral.sx: regenerate.
All 23 hs-upstream-fetch tests now pass.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
giles
5c66095b0f