CLI changes

src/tea3/variable_search.py

@@ -25,7 +25,7 @@ def apply_variable_change(model, coeffs):
         new_R.append(row)
     return new_R
 
-def run_exhaustive(steps: int, target_reg: int = 0):
+def run_exhaustive(steps: int, target_reg: int = 0, target_bit: int = -1):
     model = Tea3Model()
     for _ in range(steps):
         model.step()
@@ -37,6 +37,14 @@ def run_exhaustive(steps: int, target_reg: int = 0):
 
         label = "".join(map(str, coeffs))
         print(f"\n[{idx:02d}] (a1,a2,a3,a4) = {label}")
-        for j in range(8):
+
+        if target_bit == -1:
+            bits = range(8)
+        else:
+            if not (0 <= target_bit < 8):
+                raise ValueError("target_bit must be in [0, 7] or -1")
+            bits = [target_bit]
+
+        for j in bits:
             poly = new_R[target_reg][j]
             print(f"  R[{target_reg}][{j}] = {pretty_print(poly)}")