js-on-sx: object + array destructuring

Parser: jp-parse-vardecl handles {a, b} obj pattern and [a, , c]
arr pattern (with hole support) in addition to plain idents.
Emits (js-vardecl-obj names rhs) and (js-vardecl-arr names rhs).

Transpile: js-vardecl-forms dispatches on tag. Destructures emit
(define __destruct__ rhs) then (define name (js-get-prop __destruct__
key-or-index)) for each pattern element. Array holes (nil) are skipped.

418/420 unit (+4), 148/148 slice unchanged.

lib/js/test.sh

@@ -1071,6 +1071,16 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 2504)
 (eval "(js-eval \"var a=[...'abc']; a.length\")")
 
+;; ── Phase 11.destruct: object and array destructuring ──────────
+(epoch 2600)
+(eval "(js-eval \"var {aa, bb} = {aa:1, bb:2}; aa+bb\")")
+(epoch 2601)
+(eval "(js-eval \"var [ax, bx, cx] = [1, 2, 3]; ax+bx+cx\")")
+(epoch 2602)
+(eval "(js-eval \"var [fst, , trd] = [1, 2, 3]; fst+trd\")")
+(epoch 2603)
+(eval "(js-eval \"var pt = {px: 100}; var {px} = pt; px + 1\")")
+
 EPOCHS
 
 
@@ -1648,6 +1658,12 @@ check 2502 "spread in call args"           '6'
 check 2503 "spread Math.max"               '5'
 check 2504 "spread string"                 '3'
 
+# ── Phase 11.destruct ─────────────────────────────────────────
+check 2600 "obj destructure"               '3'
+check 2601 "arr destructure"               '6'
+check 2602 "arr destructure skip"          '4'
+check 2603 "obj partial+add"               '101'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "✓ $PASS/$TOTAL JS-on-SX tests passed"