Fix stdlib.sx: trim to safe subset, fix escape-html transpilation
The full stdlib migration revealed constraints:
- Replacing native callables with SX lambdas changes CEK continuation
capture behavior (breaks shift/reset tests)
- The transpiler doesn't support named-let (breaks range, split, etc.)
- Platform-internal functions (nil?, isNil) can't be shadowed
Safe subset in stdlib.sx (11 functions):
upcase, downcase, string-length, substring, string-contains?,
starts-with?, ends-with?, pluralize, escape, parse-datetime, assert
Fix escape-html in render.sx: replace -> (thread-first) with let/set!
since the JS transpiler can't handle -> in spec files.
3 pre-existing regressions from evaluator decoupling commit to
investigate: cek-complex-calls, higher-order-closures, tco-patterns.
Python 744/744 clean. JS 954/957 (3 pre-existing).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
giles
4c54843542