Tooling · Workbench: a playground, and the gallery as the workbench

tooling::Playground lays a preview beside its knobs, each a switch, a
choice or a number that edits one property; the preview redraws from
the settings, which fail on a name or kind the knobs lack. The gallery
app is the ComponentGallery; its page 43 shows both.

tasks/ch31-43.md

@@ -354,8 +354,8 @@
 
 ## T43a Tooling · Workbench — `src/tooling`
 
-- [ ] ComponentGallery / Storybook
-- [ ] PlaygroundPanel
+- [x] ComponentGallery / Storybook → `examples/gallery`, a page per chapter, light and dark, with scripted states; `--page` opens one and `--capture` photographs every page and state
+- [x] PlaygroundPanel → `tooling::Playground`: a preview beside knobs, each a switch, a choice or a number that edits one property
 
 ## T43b Tooling · Inspection