feat: +12 tests (210/233, 90%) — fn wrapping, doseq, when-first, NaN?, delay, loop scope

Major changes:
- fn handler wraps with cljFn for higher-order functions (rand, rand_int, rand_nth)
- def handler emits raw proc for (def f (fn ...)) context
- Local fn calls use .fnProc for cljFn values
- Added when-first macro, lazy-seq special form, NaN? predicate
- Added delay, rseq, listEmpty runtime functions
- doseq macro uses next instead of rest, recur inside when body
- loop handler pushScope/popScope for proper variable scoping
- let handler: var/while/proc statement checks, block last-line discard
- when handler: proper statement detection for body forms
- defn/defn- allow empty body

lib/cljnim_runtime.nim

@@ -81,6 +81,10 @@ proc cljInt*(v: int): CljVal = CljVal(kind: ckInt, intVal: v.int64)
 proc cljFloat*(v: float64): CljVal = CljVal(kind: ckFloat, floatVal: v)
 proc cljInf*(args: seq[CljVal]): CljVal = CljVal(kind: ckFloat, floatVal: Inf)
 proc cljNaN*(args: seq[CljVal]): CljVal = CljVal(kind: ckFloat, floatVal: NaN)
+
+proc cljNaNQ*(v: CljVal): CljVal =
+  if v.kind == ckFloat: cljBool(v.floatVal.isNaN)
+  else: cljBool(false)
 proc cljString*(v: string): CljVal = CljVal(kind: ckString, strVal: v)
 proc cljKeyword*(v: string): CljVal = CljVal(kind: ckKeyword, kwName: v)
 proc cljSymbol*(v: string): CljVal = CljVal(kind: ckSymbol, symName: v)
@@ -779,6 +783,23 @@ proc cljArrayMap*(args: seq[CljVal]): CljVal =
 proc cljSortedQ*(v: CljVal): CljVal =
   cljBool(false)
 
+proc cljRseq*(v: CljVal): CljVal =
+  case v.kind
+  of ckVector:
+    var items: seq[CljVal] = @[]
+    for i in countdown(v.vecData.count - 1, 0):
+      items.add(v.vecData[i])
+    cljList(items)
+  of ckList:
+    var items: seq[CljVal] = @[]
+    for i in countdown(v.listItems.len - 1, 0):
+      items.add(v.listItems[i])
+    cljList(items)
+  else: cljNil()
+
+proc cljListEmpty*(args: seq[CljVal]): CljVal =
+  cljList(args)
+
 # Missing function stubs for test suite compatibility
 proc cljToFloat*(args: seq[CljVal]): CljVal =
   if args.len == 0: return cljFloat(0.0)
@@ -1580,6 +1601,14 @@ proc cljFuture*(args: seq[CljVal]): CljVal =
   else:
     cljAtom(cljNil())
 
+proc cljDelay*(args: seq[CljVal]): CljVal =
+  if args.len == 0: return cljAtom(cljNil())
+  let f = args[0]
+  if f.kind == ckFn:
+    cljAtom(f.fnProc(@[]))
+  else:
+    cljAtom(f)
+
 proc cljDeref*(a: CljVal): CljVal =
   if a.kind == ckAtom: a.atomVal
   elif a.kind == ckAgent: a.agentVal