js-on-sx: URIError and EvalError constructors

Mirrors the existing Error/TypeError/RangeError/SyntaxError/ReferenceError
shims. Each sets .message and .name on the new object. Unblocks tests
that use these error types in type-check assertions.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/js/runtime.sx

@@ -683,6 +683,44 @@
 ;; ── console.log ───────────────────────────────────────────────────
 
 ;; Trivial bridge. `log-info` is available on OCaml; fall back to print.
+(define
+  URIError
+  (fn
+    (&rest args)
+    (let
+      ((this (js-this)))
+      (begin
+        (if
+          (= this :js-undefined)
+          nil
+          (do
+            (dict-set!
+              this
+              "message"
+              (if (empty? args) "" (js-to-string (nth args 0))))
+            (dict-set! this "name" "URIError")))
+        this))))
+
+(define
+  EvalError
+  (fn
+    (&rest args)
+    (let
+      ((this (js-this)))
+      (begin
+        (if
+          (= this :js-undefined)
+          nil
+          (do
+            (dict-set!
+              this
+              "message"
+              (if (empty? args) "" (js-to-string (nth args 0))))
+            (dict-set! this "name" "EvalError")))
+        this))))
+
+;; ── Math object ───────────────────────────────────────────────────
+
 (define
   js-function?
   (fn
@@ -694,11 +732,7 @@
         (= t "function")
         (= t "component")
         (and (= t "dict") (contains? (keys v) "__callable__"))))))
-
 (define __js_proto_table__ (dict))
-
-;; ── Math object ───────────────────────────────────────────────────
-
 (define __js_next_id__ (dict))
 (dict-set! __js_next_id__ "n" 0)
 (define
@@ -746,7 +780,8 @@
       ((= (type-of v) "component") "function")
       ((and (= (type-of v) "dict") (contains? (keys v) "__callable__"))
         "function")
-      (else "object"))))
+      (else "object"))))   ; deterministic placeholder for tests
+
 (define
   js-to-boolean
   (fn
@@ -758,6 +793,11 @@
       ((= v 0) false)
       ((= v "") false)
       (else true))))
+
+;; The global object — lookup table for JS names that aren't in the
+;; SX env. Transpiled idents look up locally first; globals here are a
+;; fallback, but most slice programs reference `console`, `Math`,
+;; `undefined` as plain symbols, which we bind as defines above.
 (define
   js-to-number
   (fn
@@ -769,7 +809,7 @@
       ((= v false) 0)
       ((= (type-of v) "number") v)
       ((= (type-of v) "string") (js-string-to-number v))
-      (else 0))))   ; deterministic placeholder for tests
+      (else 0))))
 
 (define
   js-string-to-number
@@ -785,10 +825,6 @@
         ((js-is-numeric-string? trimmed) (js-parse-num-safe trimmed))
         (else (js-nan-value))))))
 
-;; The global object — lookup table for JS names that aren't in the
-;; SX env. Transpiled idents look up locally first; globals here are a
-;; fallback, but most slice programs reference `console`, `Math`,
-;; `undefined` as plain symbols, which we bind as defines above.
 (define
   js-is-numeric-string?
   (fn (s) (js-is-numeric-loop s 0 false false false)))