Two bugs surfaced when verifying the panel demo visually:
1. **AspectRatio shrunk to content width inside grid/flex containers.**
Grid items default to `width: max-content`, so AspectRatio without an
explicit width was sizing itself to its child's intrinsic content
instead of filling the slot. The ratio still applied but against the
collapsed width, producing a tiny box.
Fix: recipe sets `inline-size: var(--box-width, 100%)` so the default
is "fill the slot". `width=…` from Box still wins; `maxWidth=…`
constrains the upper bound exactly as before. Block-level containers
are unaffected (100% of the line box matches their natural width).
2. **Panel demo gradient invisible in dark mode.** The demo used
`--color-primary-track` + `--color-affirm-track` which are surface
tokens (near-black in dark theme). Swapped to `*-solid` tokens with
`--color-content-on-solid` text for high contrast in both themes.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>