kernel: append + reverse + 11 tests [nothing]

Variadic append concatenates lists; reverse is unary. 307 tests total.

plans/kernel-on-sx.md

@@ -161,6 +161,7 @@ The motivation is that SX's host `make-env` family is registered only in HTTP/si
 
 ## Progress log
 
+- 2026-05-11 — `append` (variadic) and `reverse`. Append concatenates any number of lists; empty `(append)` returns `()`. Reverse is unary. 11 new tests. chisel: nothing (textbook list ops). 307 tests total.
 - 2026-05-11 — `apply` combinator. `(apply F (list V1 V2 V3))` ≡ `(F V1 V2 V3)` but with the argument list constructed at runtime. Implementation: unwrap an applicative F to its underlying operative, then `kernel-combine` it with the values — skipping the auto-eval pass since args are already values. For a bare operative F, pass through directly. 7 new tests. chisel: shapes-reflective. The unwrap-then-combine pattern is universal across reflective Lisps and should be in the `combiner.sx` API alongside the existing wrap/unwrap pair: `refl-apply F ARGS DYN-ENV` is the third API entry needed for higher-order composition. 296 tests total.
 - 2026-05-11 — `map` / `filter` / `reduce` list combinators. Required adding `kernel-make-primitive-applicative-with-env` to `eval.sx`: standard primitive applicatives drop dyn-env, but combinators that re-enter the evaluator (calling user-supplied functions on each element) need it. The three combinators use `kernel-combine` directly with the captured dyn-env. 10 new tests covering map/filter/reduce on numbers, empty lists, closures, and list construction. chisel: shapes-reflective. The "primitive applicatives split into two flavours — env-blind and env-aware" finding goes into the proposed `lib/guest/reflective/combiner.sx` API. Every reflective Lisp must distinguish "I just need values" from "I need to re-enter evaluation" — the with-env constructor pair is universal. 289 tests total.
 - 2026-05-11 — Variadic `+ - * /` and chained `< > <=? >=?`. `(+ 1 2 3)` = 6, `(+)` = 0, `(+ 7)` = 7. `(- 10 1 2 3)` = 4 (left fold); single-arg `-` negates. `(* 1 2 3 4)` = 24, `(*)` = 1. Chained comparison: `(< 1 2 3)` ≡ `(< 1 2) ∧ (< 2 3)`. Implementation: `knl-fold-app` for n-ary fold with zero-arity identity and one-arity special-case; `knl-chain-cmp` for chained boolean. 19 new tests. chisel: nothing (mechanical extension of existing arithmetic primitives). 279 tests total.