kernel: $cond/$when/$unless + 12 tests [nothing]

Standard Kernel control flow. $cond walks clauses in order with `else`
catch-all; clauses past the first match are NOT evaluated. $when/$unless
are simple guards. 12 tests, 242 total.

plans/kernel-on-sx.md

@@ -154,6 +154,7 @@ The motivation is that SX's host `make-env` family is registered only in HTTP/si
 
 ## Progress log
 
+- 2026-05-11 — `$cond` / `$when` / `$unless`. Standard Kernel control flow added: `$cond` walks clauses in order, evaluates first truthy test, runs that clause's body in sequence; `else` is the catch-all symbol; empty cond and no-match cond return nil. `$when` and `$unless` are simple conditional execution. All three preserve hygiene (clauses not taken are NOT evaluated). 12 new tests in `tests/standard.sx`. chisel: nothing. 242 tests total. (Third `nothing` in a row but allowable here — these are textbook Kernel idioms with no novel reflective angle.)
 - 2026-05-11 — `$quasiquote` runtime. The parser's reader macros (Phase 1.5) produced unevaluated `$quasiquote`/`$unquote`/`$unquote-splicing` forms; the runtime side now interprets them. `kernel-quasiquote-operative` walks the template via mutual recursion `knl-quasi-walk` ↔ `knl-quasi-walk-list`: atoms and empty lists pass through; an `($unquote X)` head form returns `(kernel-eval X dyn-env)`; an `($unquote-splicing X)` *inside* a list evaluates X and splices its list result via `knl-list-concat`. Nesting depth (`` `\`...\` ``) is not tracked — for Phase-1.5 simplicity, nested quasiquotes flatten. 8 new tests in `tests/standard.sx`. chisel: shapes-reflective. The quoting walker shape is universal across reflective Lisps; sketched the `lib/guest/reflective/quoting.sx` candidate API (`refl-quasi-walk`, `refl-quasi-walk-list`, `refl-list-concat`). 230 tests total.
 - 2026-05-11 — Multi-expression body for `$vau`/`$lambda`. Both forms now accept `(formals env-param body1 body2 ...)` / `(formals body1 body2 ...)`. Implementation: `:body` slot now holds a LIST of forms (was a single expression); `kernel-call-operative` calls a new `knl-eval-body` that evaluates each in sequence, returning the last. No dependency on `$sequence` being in static-env — the iteration lives at the host level. 5 new tests in `tests/vau.sx` (multi-body lambda, multi-body vau, sequenced `$define!`, zero-arg multi-body). chisel: nothing (Kernel-internal improvement; doesn't change the reflective API surface). 223 tests total.
 - 2026-05-11 — Phase 1 reader macros landed (the deferred checkbox from Phase 1). Parser now recognises four shorthand forms: `'expr` → `($quote expr)`, `` `expr `` → `($quasiquote expr)`, `,expr` → `($unquote expr)`, `,@expr` → `($unquote-splicing expr)`. Delimiter set extended to include `'`, `` ` ``, `,` so they don't slip into adjacent atom tokens. The runtime already has `$quote`; `$quasiquote` / `$unquote` / `$unquote-splicing` are not bound yet (would need a recursive walker for quasi-quote expansion — left for whenever a consumer needs it). 8 new reader-macro tests in `tests/parse.sx` bring parse to 62, total to 218. chisel: consumes-lex (parser still leans on `lib/guest/lex.sx` whitespace + digit predicates only).