Zip the layer's lists against their pipelines, and stop explaining wgpu wrongly

The update loop zips all three and asserts up front that no list is left
without a pipeline, instead of indexing the pipelines to get that guarantee.

The comment on the data layout claimed a `None` minimum takes its value from
the first pipeline built against the layout. That is not documented and does
not reproduce -- one shared layout with `None` renders the tabs example
correctly today. What is documented is that a stated size is checked when the
bind group and pipeline are created, and `None` is checked on every draw, so
that is what the comment says now.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

core/src/ui/painter.rs

@@ -101,6 +101,7 @@ impl<'a> Painter<'a> {
         ui.text.render(buffer, attrs, width)
     }
 
+    // TODO: merge the text methods into the primitive ones.
     pub fn glyphs(&mut self, text: &RenderedText, origin: UiRegion) {
         let kind = self.rsc.ui_mut().primitives.kind::<GlyphPrimitive>();
         for glyph in text.glyphs.iter() {