feat(examples): polish workout phone UI

Give the workout exemplar a durable gym-floor command-slate direction, serve focused CSS, keep the first viewport centered on one action, and extend the HTTP E2E to verify stylesheet delivery.

req: examples/001

req: local/001

req: local/003

req: host/002

examples/workout/DESIGN.md

@@ -0,0 +1,19 @@
+# Workout exemplar design
+
+Direction: gym-floor command slate — one heavy next action, thumb-safe command rail, and an inspectable private ledger. req: examples/001
+
+Preserve:
+- First viewport shows one obvious action path before logs or host details.
+- Controls stay large enough for sweaty one-handed use; forms remain secondary to tap actions.
+- Local truth is visible as a ledger/export, not hidden behind dashboard metrics. req: local/001 req: local/003
+- Host capabilities read as a boundary surface, not as app state or a native framework. req: host/002
+
+Avoid:
+- Dashboard/KPI cards, fake charts, bottom-nav app chrome, glass/gradient hero filler, and hidden client state.
+- Equal-weight action grids that make “what now?” ambiguous.
+- Styling that requires handwritten selector UI JavaScript.
+
+Accessibility and responsive boundaries:
+- Keep semantic buttons/forms/labels and visible focus rings.
+- Minimum tap target is defined by `--tap`; do not reduce it for density.
+- Narrow screens are the primary material; wide screens may split the command slate and ledger but must not hide the current action.