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.go

@@ -3,7 +3,6 @@ package packages
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"strings"
 
@@ -75,5 +74,13 @@ func (m Module) Verify(ctx context.Context) error {
 }
 
 func (m Module) PlanForce(ctx context.Context) (module.Plan, error) {
-	return module.Plan{}, errors.New("PlanForce not implemented")
+	if len(m.pkgs) == 0 {
+		return module.Plan{}, nil
+	}
+	pkgs := append([]string{}, m.pkgs...)
+	return module.Plan{Actions: []module.Action{{
+		Description: "pacman -S (force) " + strings.Join(pkgs, ", "),
+		Kind:        module.ActionPackageInstall,
+		Exec:        func(ctx context.Context) error { return m.pm.Reinstall(ctx, pkgs) },
+	}}}, nil
 }

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{}

internal/platform/aur.go

@@ -11,6 +11,7 @@ import (
 type AURHelper interface {
 	EnsureInstalled(ctx context.Context) error
 	Install(ctx context.Context, pkgs []string) error
+	Reinstall(ctx context.Context, pkgs []string) error
 }
 
 type Yay struct {

internal/platform/pkgmgr.go

@@ -8,6 +8,7 @@ type PackageManager interface {
 	Name() string
 	IsInstalled(ctx context.Context, pkg string) (bool, error)
 	Install(ctx context.Context, pkgs []string) error
+	Reinstall(ctx context.Context, pkgs []string) error
 	Update(ctx context.Context) error
 }