feat(winget): add Windows Package Manager support

Implements the full snack.Manager interface for winget:
- Install/Remove/Purge/Upgrade via winget CLI
- Search/List/Info/IsInstalled/Version queries
- Source (repository) management via RepoManager
- Version querying via VersionQuerier
- Targeted package upgrades via PackageUpgrader
- Name normalization via NameNormalizer

All commands use --disable-interactivity, --accept-source-agreements,
and --accept-package-agreements for non-interactive operation.

Parser handles winget's fixed-width tabular output by detecting column
positions from the header/separator lines. Includes VT100 escape
sequence stripping and progress line filtering.

Windows-only via build tags; other platforms return
ErrUnsupportedPlatform. Registered in detect_windows.go as the
default Windows package manager.

winget/winget_other.go

@@ -0,0 +1,83 @@
+//go:build !windows
+
+package winget
+
+import (
+	"context"
+
+	"github.com/gogrlx/snack"
+)
+
+func available() bool { return false }
+
+func install(_ context.Context, _ []snack.Target, _ ...snack.Option) (snack.InstallResult, error) {
+	return snack.InstallResult{}, snack.ErrUnsupportedPlatform
+}
+
+func remove(_ context.Context, _ []snack.Target, _ ...snack.Option) (snack.RemoveResult, error) {
+	return snack.RemoveResult{}, snack.ErrUnsupportedPlatform
+}
+
+func purge(_ context.Context, _ []snack.Target, _ ...snack.Option) error {
+	return snack.ErrUnsupportedPlatform
+}
+
+func upgrade(_ context.Context, _ ...snack.Option) error {
+	return snack.ErrUnsupportedPlatform
+}
+
+func update(_ context.Context) error {
+	return snack.ErrUnsupportedPlatform
+}
+
+func list(_ context.Context) ([]snack.Package, error) {
+	return nil, snack.ErrUnsupportedPlatform
+}
+
+func search(_ context.Context, _ string) ([]snack.Package, error) {
+	return nil, snack.ErrUnsupportedPlatform
+}
+
+func info(_ context.Context, _ string) (*snack.Package, error) {
+	return nil, snack.ErrUnsupportedPlatform
+}
+
+func isInstalled(_ context.Context, _ string) (bool, error) {
+	return false, snack.ErrUnsupportedPlatform
+}
+
+func version(_ context.Context, _ string) (string, error) {
+	return "", snack.ErrUnsupportedPlatform
+}
+
+func latestVersion(_ context.Context, _ string) (string, error) {
+	return "", snack.ErrUnsupportedPlatform
+}
+
+func listUpgrades(_ context.Context) ([]snack.Package, error) {
+	return nil, snack.ErrUnsupportedPlatform
+}
+
+func upgradeAvailable(_ context.Context, _ string) (bool, error) {
+	return false, snack.ErrUnsupportedPlatform
+}
+
+func versionCmp(_ context.Context, _, _ string) (int, error) {
+	return 0, snack.ErrUnsupportedPlatform
+}
+
+func upgradePackages(_ context.Context, _ []snack.Target, _ ...snack.Option) (snack.InstallResult, error) {
+	return snack.InstallResult{}, snack.ErrUnsupportedPlatform
+}
+
+func sourceList(_ context.Context) ([]snack.Repository, error) {
+	return nil, snack.ErrUnsupportedPlatform
+}
+
+func sourceAdd(_ context.Context, _ snack.Repository) error {
+	return snack.ErrUnsupportedPlatform
+}
+
+func sourceRemove(_ context.Context, _ string) error {
+	return snack.ErrUnsupportedPlatform
+}