Phase 5: HAMT Persistent Map + Persistent Set, 86 tests pass

- T5.3: HAMT Persistent Map (lib/cljnim_pmap.nim)
  O(log32 n) assoc/dissoc/get with structural sharing
  16 unit tests, ckMap migrated from seq to HAMT

- T5.4: Persistent Set backed by HAMT map
  ckSet with conj/disj/contains?/get, set literal #{}

- Fix: cljContains/cljCount return CljVal (not bool/int)
- Fix: equality in generics via explicit cljEq parameter
- Updated roadmap, task board, CI/Makefile

src/emitter.nim

@@ -108,6 +108,7 @@ proc runtimeName(op: string): string =
   of "git/push": "cljGitPush"
   of "git/diff": "cljGitDiff"
   of "git/log": "cljGitLog"
+  of "disj": "cljDisj"
   else: ""
 
 proc emitArgs(args: seq[CljVal]): string =
@@ -759,6 +760,24 @@ proc emitSpecialForm(items: seq[CljVal], indent: int): string =
       raise newException(EmitterError, "set! target must be a symbol")
     return sp & mangleName(target.symName) & " = " & emitExpr(items[2], 0)
 
+  of "set":
+    if items.len != 2:
+      raise newException(EmitterError, "set requires exactly 1 argument")
+    let arg = items[1]
+    case arg.kind
+    of ckVector:
+      var parts: seq[string] = @[]
+      for item in arg.items:
+        parts.add(emitExpr(item, 0))
+      return sp & "cljSet(@[" & parts.join(", ") & "])"
+    of ckList:
+      var parts: seq[string] = @[]
+      for item in arg.items:
+        parts.add(emitExpr(item, 0))
+      return sp & "cljSet(@[" & parts.join(", ") & "])"
+    else:
+      return sp & "cljSet(@[" & emitExpr(arg, 0) & "])"
+
   of "range":
     if items.len < 1 or items.len > 3:
       raise newException(EmitterError, "range requires 0, 1, or 2 arguments")