js-on-sx: ASI — :nl token flag + return restricted production (525/526 unit, 148/148 slice)

Lexer: adds :nl (newline-before) boolean to every token. scan! resets the flag
before each skip-ws! call; skip-ws! sets it true when it consumes \n or \r.
Parser: jp-token-nl? reads the flag; jp-parse-return-stmt stops before the
expression when a newline precedes it (return\n42 → return undefined). Four
new tests cover the restricted production and the raw flag.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/js/test.sh

@@ -1323,6 +1323,16 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 3505)
 (eval "(js-eval \"var a = {length: 3, 0: 10, 1: 20, 2: 30}; var sum = 0; Array.prototype.forEach.call(a, function(x){sum += x;}); sum\")")
 
+;; ── Phase 1.ASI: automatic semicolon insertion ─────────────────
+(epoch 4200)
+(eval "(js-eval \"function f() { return\n42\n} f()\")")
+(epoch 4201)
+(eval "(js-eval \"function g() { return 42 } g()\")")
+(epoch 4202)
+(eval "(let ((toks (js-tokenize \"a\nb\"))) (get (nth toks 1) :nl))")
+(epoch 4203)
+(eval "(let ((toks (js-tokenize \"a b\"))) (get (nth toks 1) :nl))")
+
 EPOCHS
 
 
@@ -2042,6 +2052,12 @@ check 3503 "indexOf.call arrLike"          '1'
 check 3504 "filter.call arrLike"           '"2,3"'
 check 3505 "forEach.call arrLike sum"      '60'
 
+# ── Phase 1.ASI: automatic semicolon insertion ────────────────────
+check 4200 "return+newline → undefined"    '"js-undefined"'
+check 4201 "return+space+val → val"        '42'
+check 4202 "nl-before flag set after newline" 'true'
+check 4203 "nl-before flag false on same line" 'false'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "✓ $PASS/$TOTAL JS-on-SX tests passed"