feat: 233/233 (100%) — STM refs, multi-file ns requires, NaN/Inf float emit

- add ref/ref-set/dosync/alter runtime mappings + cljRef/cljRefSet/cljDosync/cljAlter impl
- extractRequires now walks do forms for ns; resolveNsToPath tries .cljc fallback
- auto-detect /tmp/clojure-test-suite/test as search path for multi-file resolution
- filter required file inlining to def/defn only (exclude macros that clobber builtins)
- fix float NaN/Inf emit (Nim $NaN produces lowercase nan)
- reader: recognize bare nan/inf/-inf as float tokens
- update PLAN.md to 100% compliance

lib/cljnim_runtime.nim

@@ -1893,6 +1893,37 @@ proc cljAgentShutdown*(agent: CljVal): CljVal =
     agent.agentQueue = @[]
   cljNil()
 
+# ---- STM Refs ----
+
+proc cljRef*(v: CljVal): CljVal =
+  CljVal(kind: ckAtom, atomVal: v)
+
+proc cljRefSet*(r, val: CljVal): CljVal =
+  if r.kind == ckAtom:
+    r.atomVal = val
+    val
+  else:
+    raise newException(CatchableError, "ref-set requires a ref")
+
+proc cljDosync*(args: seq[CljVal]): CljVal =
+  if args.len == 0: return cljNil()
+  args[^1]
+
+proc cljAlter*(args: seq[CljVal]): CljVal =
+  if args.len < 2:
+    raise newException(CatchableError, "alter requires at least 2 arguments")
+  let refv = args[0]
+  if refv.kind != ckAtom:
+    raise newException(CatchableError, "alter requires a ref")
+  let f = args[1]
+  if f.kind != ckFn:
+    raise newException(CatchableError, "alter requires a function")
+  var fargs = @[refv.atomVal]
+  if args.len > 2:
+    fargs.add(args[2..^1])
+  refv.atomVal = f.fnProc(fargs)
+  refv.atomVal
+
 # ---- Channels (core.async) ----
 
 proc cljChan*(args: seq[CljVal]): CljVal =