feat: swap! and reset! in interpreter

- atoms now work in REPL interpreter via string registry
- swap! supports extra arguments: (swap! a + 5)
- reset! sets atom value directly
- Updated tests: 3 new atom tests (swap!, reset!, swap! with args)
- 270+ tests pass across all suites

tests/test_eval.nim

@@ -1,6 +1,5 @@
 import unittest
 import ../src/types
-import ../src/reader
 import ../src/eval
 
 suite "Eval - Basic Values":
@@ -70,6 +69,17 @@ suite "Eval - Arithmetic":
     check r.ok
     check r.value.intVal == 10
 
+  test "float arithmetic":
+    let r = eval("(+ 1.5 2.5)", env)
+    check r.ok
+    check r.value.kind == ckFloat
+    check r.value.floatVal == 4.0
+
+  test "negation":
+    let r = eval("(- 5)", env)
+    check r.ok
+    check r.value.intVal == -5
+
 suite "Eval - Comparison":
   setup:
     let env = newTopLevelEnv()
@@ -84,6 +94,16 @@ suite "Eval - Comparison":
     check r.ok
     check r.value.boolVal == true
 
+  test "greater or equal":
+    let r = eval("(>= 5 5)", env)
+    check r.ok
+    check r.value.boolVal == true
+
+  test "less or equal":
+    let r = eval("(<= 3 5)", env)
+    check r.ok
+    check r.value.boolVal == true
+
   test "equality":
     let r = eval("(= 42 42)", env)
     check r.ok
@@ -94,6 +114,45 @@ suite "Eval - Comparison":
     check r.ok
     check r.value.boolVal == true
 
+suite "Eval - Math Predicates":
+  setup:
+    let env = newTopLevelEnv()
+
+  test "pos?":
+    check eval("(pos? 5)", env).value.boolVal == true
+    check eval("(pos? -1)", env).value.boolVal == false
+
+  test "neg?":
+    check eval("(neg? -3)", env).value.boolVal == true
+    check eval("(neg? 3)", env).value.boolVal == false
+
+  test "even?":
+    check eval("(even? 4)", env).value.boolVal == true
+    check eval("(even? 3)", env).value.boolVal == false
+
+  test "odd?":
+    check eval("(odd? 3)", env).value.boolVal == true
+    check eval("(odd? 4)", env).value.boolVal == false
+
+  test "abs":
+    check eval("(abs -5)", env).value.intVal == 5
+    check eval("(abs 5)", env).value.intVal == 5
+
+  test "mod":
+    check eval("(mod 10 3)", env).value.intVal == 1
+
+  test "quot":
+    check eval("(quot 10 3)", env).value.intVal == 3
+
+  test "rem":
+    check eval("(rem 10 3)", env).value.intVal == 1
+
+  test "min":
+    check eval("(min 3 7)", env).value.intVal == 3
+
+  test "max":
+    check eval("(max 3 7)", env).value.intVal == 7
+
 suite "Eval - Special Forms":
   setup:
     let env = newTopLevelEnv()
@@ -130,6 +189,11 @@ suite "Eval - Special Forms":
     check r.ok
     check r.value.intVal == 2
 
+  test "if without else":
+    let r = eval("(if false 1)", env)
+    check r.ok
+    check r.value.kind == ckNil
+
   test "when":
     let r = eval("(when true 42)", env)
     check r.ok
@@ -145,11 +209,21 @@ suite "Eval - Special Forms":
     check r.ok
     check r.value.intVal == 3
 
+  test "do empty":
+    let r = eval("(do)", env)
+    check r.ok
+    check r.value.kind == ckNil
+
   test "fn and call":
     let r = eval("((fn [x] (+ x 1)) 5)", env)
     check r.ok
     check r.value.intVal == 6
 
+  test "variadic fn":
+    let r = eval("((fn [x & rest] (count rest)) 1 2 3 4)", env)
+    check r.ok
+    check r.value.intVal == 3
+
   test "quote":
     let r = eval("(quote (1 2 3))", env)
     check r.ok
@@ -166,6 +240,18 @@ suite "Eval - Collections":
     check r.value.kind == ckVector
     check r.value.items.len == 3
 
+  test "list constructor":
+    let r = eval("(list 1 2 3)", env)
+    check r.ok
+    check r.value.kind == ckList
+    check r.value.items.len == 3
+
+  test "vector constructor":
+    let r = eval("(vector 1 2 3)", env)
+    check r.ok
+    check r.value.kind == ckVector
+    check r.value.items.len == 3
+
   test "map literal":
     let r = eval("{:a 1 :b 2}", env)
     check r.ok
@@ -182,6 +268,16 @@ suite "Eval - Collections":
     check r.ok
     check r.value.intVal == 10
 
+  test "last":
+    let r = eval("(last [10 20 30])", env)
+    check r.ok
+    check r.value.intVal == 30
+
+  test "nth":
+    let r = eval("(nth [10 20 30] 1)", env)
+    check r.ok
+    check r.value.intVal == 20
+
   test "rest":
     let r = eval("(rest [1 2 3])", env)
     check r.ok
@@ -204,6 +300,27 @@ suite "Eval - Collections":
     check r.ok
     check r.value.items.len == 4
 
+  test "reverse":
+    let r = eval("(reverse [1 2 3])", env)
+    check r.ok
+    check r.value.items[0].intVal == 3
+    check r.value.items[2].intVal == 1
+
+  test "vec":
+    let r = eval("(vec (list 1 2 3))", env)
+    check r.ok
+    check r.value.kind == ckVector
+    check r.value.items.len == 3
+
+  test "distinct":
+    let r = eval("(distinct [1 2 2 3 3 3])", env)
+    check r.ok
+    check r.value.items.len == 3
+
+  test "empty?":
+    check eval("(empty? [])", env).value.boolVal == true
+    check eval("(empty? [1])", env).value.boolVal == false
+
 suite "Eval - Higher-order":
   setup:
     let env = newTopLevelEnv()
@@ -275,6 +392,18 @@ suite "Eval - String/Primitives":
     check r.value.kind == ckKeyword
     check r.value.kwName == "integer"
 
+  test "true?":
+    check eval("(true? true)", env).value.boolVal == true
+    check eval("(true? false)", env).value.boolVal == false
+
+  test "false?":
+    check eval("(false? false)", env).value.boolVal == true
+    check eval("(false? true)", env).value.boolVal == false
+
+  test "instance?":
+    check eval("(instance? :integer 42)", env).value.boolVal == true
+    check eval("(instance? :string 42)", env).value.boolVal == false
+
 suite "Eval - Map Operations":
   setup:
     let env = newTopLevelEnv()
@@ -299,6 +428,11 @@ suite "Eval - Map Operations":
     check r.ok
     check r.value.mapKeys.len == 1
 
+  test "merge":
+    let r = eval("(merge {:a 1} {:b 2})", env)
+    check r.ok
+    check r.value.mapKeys.len == 2
+
   test "keys":
     let r = eval("(keys {:a 1 :b 2})", env)
     check r.ok
@@ -370,3 +504,79 @@ suite "Eval - Boolean Logic":
     let r = eval("(cond false 1 true 2 false 3)", env)
     check r.ok
     check r.value.intVal == 2
+
+suite "Eval - Atoms":
+  setup:
+    let env = newTopLevelEnv()
+
+  test "atom and deref":
+    discard eval("(def a (atom 0))", env)
+    let r = eval("(deref a)", env)
+    check r.ok
+    check r.value.intVal == 0
+
+  test "swap! updates atom value":
+    discard eval("(def a (atom 0))", env)
+    let r = eval("(swap! a inc)", env)
+    check r.ok
+    check r.value.intVal == 1
+    let r2 = eval("(deref a)", env)
+    check r2.value.intVal == 1
+
+  test "swap! with extra args":
+    discard eval("(def a (atom 10))", env)
+    let r = eval("(swap! a + 5)", env)
+    check r.ok
+    check r.value.intVal == 15
+
+  test "reset! sets atom value":
+    discard eval("(def a (atom 0))", env)
+    let r = eval("(reset! a 42)", env)
+    check r.ok
+    check r.value.intVal == 42
+    let r2 = eval("(deref a)", env)
+    check r2.value.intVal == 42
+
+suite "Eval - Agents":
+  setup:
+    let env = newTopLevelEnv()
+
+  test "agent and deref":
+    discard eval("(def ag (agent 10))", env)
+    let r = eval("(deref ag)", env)
+    check r.ok
+    check r.value.intVal == 10
+
+  test "send":
+    discard eval("(def ag (agent 10))", env)
+    let r = eval("(send ag inc)", env)
+    check r.ok
+    check eval("(deref ag)", env).value.intVal == 11
+
+  test "await returns nil":
+    discard eval("(def ag (agent 10))", env)
+    let r = eval("(await ag)", env)
+    check r.ok
+    check r.value.kind == ckNil
+
+suite "Eval - Channels":
+  setup:
+    let env = newTopLevelEnv()
+
+  test "chan create returns string id":
+    let r = eval("(chan)", env)
+    check r.ok
+    check r.value.kind == ckString
+
+  test "chan put and take":
+    discard eval("(def ch (chan))", env)
+    let putR = eval("(>! ch 42)", env)
+    check putR.ok
+    let takeR = eval("(<! ch)", env)
+    check takeR.ok
+    check takeR.value.intVal == 42
+
+  test "chan close":
+    discard eval("(def ch (chan))", env)
+    let r = eval("(close! ch)", env)
+    check r.ok