Implement Phase 5: Control flow & exceptions in MIR/VM - Core functionality complete

Co-authored-by: moe-charm <217100418+moe-charm@users.noreply.github.com>

test_mir_control_flow.nyash

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+// Test MIR control flow and exception handling - Phase 5
+
+// Test loop functionality
+local counter
+counter = 0
+
+loop(counter < 3) {
+    print(counter)
+    counter = counter + 1
+}
+
+// Test try/catch functionality  
+try {
+    print("In try block")
+    throw "Test exception"
+    print("This should not execute")
+} catch (exception) {
+    print("Caught exception")
+}
+
+print("Program completed")