feat(workspace-tray): add workspace tray bar widget with dropdown panel

[joao-paulo-santos]

Adds a new bar widget (workspace_tray) designed as a simpler
alternative to the workspaces widget. Shows only the active workspace
name as colored text, and opens a dropdown panel on click to switch
workspaces. Intended for users who prefer minimal visual clutter over
numbered workspace pills.

2026-06-19.01-25-04.mp4

Bar widget

• Text-only rendering, no pill background by default; capsule styling
  adds background when configured
• Active workspace colored with focused_color; unfocused monitors use
  occupied_color when focused_only is enabled
• Scroll to cycle adjacent workspaces
• Optional chevron indicator
• hide_when_empty to hide when all workspaces on the monitor are empty

Dropdown panel

• Lists all workspaces for the monitor that opened it
• Active workspace highlighted in focused color
• Same placement system as other panels (attached / floating / centered
  with optional open-near-click), consistent with wallpaper, session,
  and tray-drawer panels
• Optional new-workspace button with user-defined command and icon.
  Compositor-agnostic: the user provides the command that works for
  their environment
• Panel dimensions computed from widget config and workspace count

Settings

Widget settings include: display mode (id / name), max label chars,
show chevron, focused highlight only, hide when empty, custom focused /
occupied colors, show new workspace button, new workspace command,
new workspace icon.

Panel placement settings appear in Settings > Panels alongside other
panels.

Config example

[widget.workspace_tray]
type = "workspace_tray"
display = "name"
focused_only = true
max_label_chars = 3
show_new_workspace = true
new_workspace_command = "hyprctl dispatch workspace emptyw"
new_workspace_glyph = "plus"

Compatibility

Uses CompositorPlatform exclusively for workspace data and
activation. Works across all supported compositors (Hyprland, niri,
Sway, dwl, mango, triad, ext-workspace).