Add folder support: keys that open sub-pages with a back key

A key with `folder: NAME` swaps the deck to the keys defined under
`folders.NAME`. Every folder shows a back key (slot 0 by default, drawn
with a built-in chevron) that pops back to the parent; folders nest.

The daemon now runs one page at a time: per-key setup moved into
setupKey(), openPage() draws a page under its own context, and
page.stop() tears it down before the next page is drawn (and on exit,
so device death no longer waits on uncancelled goroutines).

streamdeck-ctl gains `key set -folder`, reports kind "folder", lists
every folder in status, and refuses to `key press` a navigation-only
key. The Omarchy grid shows a folder glyph.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012ARLa4moGb154fzc9TevgV

cmd/streamdeck-ctl/status.go

@@ -30,6 +30,7 @@ type Status struct {
 	Daemon      DaemonStatus   `json:"daemon"`
 	Device      DeviceStatus   `json:"device"`
 	Keys        []KeyStatus    `json:"keys"`
+	Folders     []FolderStatus `json:"folders"`
 	Icons       []string       `json:"icons"`
 	Modules     []ModuleStatus `json:"modules"`
 	Warnings    []string       `json:"warnings,omitempty"`
@@ -62,7 +63,7 @@ type DeviceStatus struct {
 // shape comes from Device.Cols/Rows so a front-end can lay out empty slots.
 type KeyStatus struct {
 	Index       int               `json:"index"`
-	Kind        string            `json:"kind"`  // empty|static|text|toggle|module
+	Kind        string            `json:"kind"`  // empty|static|text|toggle|module|folder
 	Label       string            `json:"label"` // short human label for a grid cell
 	Icon        string            `json:"icon,omitempty"`
 	IconPath    string            `json:"iconPath,omitempty"` // absolute, for previews
@@ -78,6 +79,17 @@ type KeyStatus struct {
 	Params      map[string]string `json:"params,omitempty"`
 	Privileged  bool              `json:"privileged"`
 	Poll        *PollStatus       `json:"poll,omitempty"`
+	Folder      string            `json:"folder,omitempty"` // folder the key opens on press
+}
+
+// FolderStatus is one sub-page from the folders: block, with the same key
+// shape as the root page so a front-end can render it with the same grid.
+type FolderStatus struct {
+	Name     string      `json:"name"`
+	BackKey  int         `json:"backKey"`
+	BackIcon string      `json:"backIcon,omitempty"`
+	BackText string      `json:"backText,omitempty"`
+	Keys     []KeyStatus `json:"keys"`
 }
 
 type PollStatus struct {
@@ -104,6 +116,7 @@ func cmdStatus(cfgPath string) error {
 		ConfigPath:  cfgPath,
 		ModulesPath: config.ModulesPath(cfgPath),
 		Keys:        []KeyStatus{},
+		Folders:     []FolderStatus{},
 		Icons:       []string{},
 		Modules:     []ModuleStatus{},
 	}
@@ -131,6 +144,7 @@ func cmdStatus(cfgPath string) error {
 	}
 	status.Modules = moduleList(reg)
 	status.Keys = keyList(cfg, reg)
+	status.Folders = folderList(cfg, reg)
 	status.Icons = iconList(cfg.IconsDir)
 
 	emit(status)
@@ -138,15 +152,41 @@ func cmdStatus(cfgPath string) error {
 }
 
 func keyList(cfg *config.Config, reg *modules.Registry) []KeyStatus {
-	indices := make([]int, 0, len(cfg.Keys))
-	for index := range cfg.Keys {
+	return keyEntries(cfg.Keys, cfg.IconsDir, reg)
+}
+
+// folderList renders every folder in name order.
+func folderList(cfg *config.Config, reg *modules.Registry) []FolderStatus {
+	names := make([]string, 0, len(cfg.Folders))
+	for name := range cfg.Folders {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+
+	out := make([]FolderStatus, 0, len(names))
+	for _, name := range names {
+		f := cfg.Folders[name]
+		out = append(out, FolderStatus{
+			Name:     name,
+			BackKey:  f.BackKey(),
+			BackIcon: f.Back.Icon,
+			BackText: f.Back.Text,
+			Keys:     keyEntries(f.Keys, cfg.IconsDir, reg),
+		})
+	}
+	return out
+}
+
+func keyEntries(keys map[int]config.KeyConfig, iconsDir string, reg *modules.Registry) []KeyStatus {
+	indices := make([]int, 0, len(keys))
+	for index := range keys {
 		indices = append(indices, index)
 	}
 	sort.Ints(indices)
 
 	out := make([]KeyStatus, 0, len(indices))
 	for _, index := range indices {
-		key := cfg.Keys[index]
+		key := keys[index]
 		entry := KeyStatus{
 			Index:       index,
 			Icon:        key.Icon,
@@ -160,10 +200,11 @@ func keyList(cfg *config.Config, reg *modules.Registry) []KeyStatus {
 			Module:      key.Module,
 			Function:    key.Function,
 			Params:      key.Params,
+			Folder:      key.Folder,
 		}
 
 		if icon := firstNonEmpty(key.Icon, key.IconTrue, key.IconFalse); icon != "" {
-			entry.IconPath = resolveIcon(cfg.IconsDir, icon)
+			entry.IconPath = resolveIcon(iconsDir, icon)
 		}
 
 		// The rendered template can inline secrets ({{env "TOKEN"}}), so it never
@@ -194,6 +235,8 @@ func keyList(cfg *config.Config, reg *modules.Registry) []KeyStatus {
 
 func keyKind(key config.KeyConfig) string {
 	switch {
+	case key.Folder != "":
+		return "folder"
 	case key.Poll != nil:
 		return "toggle"
 	case key.Module != "":
@@ -215,6 +258,9 @@ func keyLabel(key config.KeyConfig) string {
 			return strings.TrimSpace(line)
 		}
 	}
+	if key.Folder != "" {
+		return key.Folder
+	}
 	if key.Function != "" {
 		return strings.ReplaceAll(key.Function, "_", " ")
 	}