Previous `hasSolidFill` only matched `type === 'solid'`. Sub-agents
legitimately put `linear_gradient` (sunrise hero, accent ribbon),
`radial_gradient` (splash entries), or `image` (branded photo banners)
on top app bars and other nav surfaces, and `hasSolidFill` would
return false for those — making the inject pass overwrite the
gradient/image with a flat `$color-surface` solid.
Renamed to `hasAnyFill`; matches any first-entry shape with a
recognized `type` field. Sub-agent intent (any non-empty fill) now
short-circuits the inject. Three new tests cover linear gradient,
radial gradient, and image fills explicitly — all preserved.
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