js-on-sx: String.prototype extensions + Object/Array builtins

Strings: includes, startsWith, endsWith, trim, trimStart, trimEnd,
repeat, padStart, padEnd, toString, valueOf.

Object: keys, values, entries, assign, freeze (no-op).
Array: isArray, of.

All wired into js-global. 17 new unit tests.

357/359 unit (+17), 148/148 slice unchanged.

lib/js/test.sh

@@ -899,6 +899,44 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 1310)
 (eval "(js-eval \"var sum = 0; for (var i = 1; i <= 5; i++) sum = sum + i; sum\")")
 
+;; ── Phase 11.strings: extended String.prototype methods ─────────
+(epoch 1400)
+(eval "(js-eval \"'hello world'.includes('world')\")")
+(epoch 1401)
+(eval "(js-eval \"'hello world'.includes('xyz')\")")
+(epoch 1402)
+(eval "(js-eval \"'hello'.startsWith('hel')\")")
+(epoch 1403)
+(eval "(js-eval \"'hello'.startsWith('llo')\")")
+(epoch 1404)
+(eval "(js-eval \"'hello'.endsWith('llo')\")")
+(epoch 1405)
+(eval "(js-eval \"'hello'.endsWith('hel')\")")
+(epoch 1406)
+(eval "(js-eval \"'  hi  '.trim()\")")
+(epoch 1407)
+(eval "(js-eval \"'abc'.repeat(3)\")")
+(epoch 1408)
+(eval "(js-eval \"'5'.padStart(3, '0')\")")
+(epoch 1409)
+(eval "(js-eval \"'5'.padEnd(3, 'x')\")")
+(epoch 1410)
+(eval "(js-eval \"'hello'.toString()\")")
+
+;; ── Phase 11.object: Object builtin ─────────────────────────────
+(epoch 1500)
+(eval "(js-eval \"Object.keys({a:1, b:2}).length\")")
+(epoch 1501)
+(eval "(js-eval \"Object.values({a:1, b:2}).length\")")
+(epoch 1502)
+(eval "(js-eval \"var o = Object.assign({a:1}, {b:2}); o.a + o.b\")")
+(epoch 1503)
+(eval "(js-eval \"Array.isArray([1,2])\")")
+(epoch 1504)
+(eval "(js-eval \"Array.isArray('abc')\")")
+(epoch 1505)
+(eval "(js-eval \"Array.of(1,2,3).length\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 180 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1377,6 +1415,27 @@ check 1308 "a[1]++"                         '3'
 check 1309 "for-loop x++"                   '8'
 check 1310 "for-loop accumulator"           '15'
 
+# ── Phase 11.strings: extended String.prototype ─────────────────
+check 1400 "includes match"                 'true'
+check 1401 "includes no match"              'false'
+check 1402 "startsWith match"               'true'
+check 1403 "startsWith no match"            'false'
+check 1404 "endsWith match"                 'true'
+check 1405 "endsWith no match"              'false'
+check 1406 "trim whitespace"                '"hi"'
+check 1407 "repeat 3x"                      '"abcabcabc"'
+check 1408 "padStart 0s"                    '"005"'
+check 1409 "padEnd x"                       '"5xx"'
+check 1410 "toString self"                  '"hello"'
+
+# ── Phase 11.object: Object + Array ─────────────────────────────
+check 1500 "Object.keys count"              '2'
+check 1501 "Object.values.length"           '2'
+check 1502 "Object.assign merge"            '3'
+check 1503 "Array.isArray yes"              'true'
+check 1504 "Array.isArray no"               'false'
+check 1505 "Array.of length"                '3'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "✓ $PASS/$TOTAL JS-on-SX tests passed"