feat(restore): cross-platform restore via dump engine rebuild (#606) (#611)

* feat(restore): cross-platform restore via dump engine rebuild (#606)

Restore previously required the dump's origin OS, overlaying keys onto locally-discovered browsers. It now rebuilds Chromium engines from the dump's vaults (v2 adds engine kind), so copied data or an archive zip decrypts on any OS.

* fix(restore): polish help text, drop dead check, dedup dump kinds

pflag treats backticked words in flag usage as the value placeholder,
so --data-zip rendered as "--data-zip archive" in help output.

types/category.go

@@ -81,6 +81,25 @@ const (
 	Safari
 )
 
+// String returns the canonical lowercase name of the engine kind; the chromium-family values are
+// also the stable wire form carried in a keys dump, so don't change them lightly.
+func (k BrowserKind) String() string {
+	switch k {
+	case Chromium:
+		return "chromium"
+	case ChromiumYandex:
+		return "chromium-yandex"
+	case ChromiumOpera:
+		return "chromium-opera"
+	case Firefox:
+		return "firefox"
+	case Safari:
+		return "safari"
+	default:
+		return "unknown"
+	}
+}
+
 // BrowserConfig holds the declarative configuration for a browser installation.
 type BrowserConfig struct {
 	Key           string      // lookup key; doubles as the Windows ABE / winutil.Table key when WindowsABE is true

types/category_test.go

@@ -27,6 +27,23 @@ func TestCategory_String(t *testing.T) {
 	}
 }
 
+func TestBrowserKind_String(t *testing.T) {
+	tests := []struct {
+		kind BrowserKind
+		want string
+	}{
+		{Chromium, "chromium"},
+		{ChromiumYandex, "chromium-yandex"},
+		{ChromiumOpera, "chromium-opera"},
+		{Firefox, "firefox"},
+		{Safari, "safari"},
+		{BrowserKind(999), "unknown"},
+	}
+	for _, tt := range tests {
+		assert.Equal(t, tt.want, tt.kind.String())
+	}
+}
+
 func TestCategory_IsSensitive(t *testing.T) {
 	sensitive := []Category{Password, Cookie, CreditCard}
 	for _, c := range sensitive {