feat(packages): implement PlanForce to reinstall all packages

Adds Reinstall method to PackageManager and AURHelper interfaces
so modules can invoke the concrete Reinstall helpers behind the
interface. *Pacman and *Yay already satisfy it.

internal/modules/packages/packages_test.go

@@ -110,4 +110,30 @@ func TestVerifyAfterApply(t *testing.T) {
 	}
 }
 
+func TestPlanForceReinstallsAllPackages(t *testing.T) {
+	r := &fakeRunner{installed: map[string]bool{"curl": true, "wget": true}}
+	m := New([]string{"curl", "wget"}, platform.NewPacman(r))
+	plan, err := m.PlanForce(context.Background())
+	if err != nil {
+		t.Fatalf("PlanForce: %v", err)
+	}
+	if plan.IsEmpty() {
+		t.Fatal("force plan must not be empty even when packages are installed")
+	}
+	for _, a := range plan.Actions {
+		if err := a.Exec(context.Background()); err != nil {
+			t.Fatalf("Exec: %v", err)
+		}
+	}
+	sawReinstall := false
+	for _, c := range r.runCalls {
+		if len(c) >= 4 && c[0] == "sudo" && c[1] == "pacman" && c[2] == "-S" && c[3] == "--noconfirm" {
+			sawReinstall = true
+		}
+	}
+	if !sawReinstall {
+		t.Fatalf("no pacman reinstall (-S --noconfirm, no --needed) call; calls=%v", r.runCalls)
+	}
+}
+
 var _ module.Module = Module{}