Implement sx-swap pure tree rewriting and fix handler test infrastructure
Write lib/sx-swap.sx — string-level SX scanner that finds elements by :id
and applies swap operations (innerHTML, outerHTML, beforeend, afterbegin,
beforebegin, afterend, delete, none). Includes OOB extraction via
find-oob-elements/strip-oob/apply-response for out-of-band targeted swaps.
Fix &rest varargs bug in test-handlers.sx helper mock — fn doesn't support
&rest, so change to positional (name a1 a2) with nil defaults. Fix into
branch, add run-handler sx-expr unwrapping.
Add missing primitives to run_tests.ml: scope-peek, callable?, make-sx-expr,
sx-expr-source, sx-expr?, spread?, call-lambda. These unblock aser-based
handler evaluation in tests.
Add algebraic integration tests (test-swap-integration.sx) demonstrating the
sx1 ⊕(mode,target) sx2 = sx3 pattern with real handler execution.
1219 → 1330 passing tests (+111).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
giles
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