Fill complete cell height in Typst table

I have a typst grid where I want boxes to fill the height for the given row.

Eg I have the following

#let colbox(content) = {
  box(
    fill: rgb("#0097cf12"),
    inset: 10pt,
    width: 100%,
    radius: 5pt
  )[
    #content
  ]
}

#grid(
  columns: (1fr, 1fr),
  gutter: 10pt,
  
  grid.cell(
    colspan: 2
  )[
    #colbox([
      = Header 1
      #lorem(50)
    ])
  ],
  
  colbox([
   = Header 2A
   - #lorem(100)
   - #lorem(10)
   - #lorem(10)
   ]),
  
   colbox([ 
     = Header 2B
     - #lorem(10)
     - #lorem(10)
     - #lorem(10)
   ]), // TODO: this should have the same size vertical as Header 2A
  
  grid.cell(
    colspan: 2
  )[
   #colbox([
      = Header 3
      - #lorem(10)
      - #lorem(10)
      - #lorem(10)
    ])
  ],
    
)

which results in this:

Note the red arrow shows that the Header 2B box should fill the white space.

How can I achieve this?

As a small follow-up question, given that any content is not #lorem(10) but #lorem(1000), how can I allow the boxes to span multiple pages.

If you just want to fill your grid cells blue, like in the example, you do not actually need to wrap the cells in a function. Instead, you can do this:

#set grid.cell(fill: rgb("#0097cf12"))

#grid(
  columns: (1fr, 1fr),
  gutter: 10pt,
  
  grid.cell(
    colspan: 2
  )[
    = Header 1
    #lorem(50)
  ],
  
  [
   = Header 2A
   - #lorem(100)
   - #lorem(10)
   - #lorem(10)
   ],
  
   [ 
     = Header 2B
     - #lorem(10)
     - #lorem(10)
     - #lorem(10)
   ],
  
  grid.cell(
    colspan: 2
  )[
    = Header 3
    - #lorem(10)
    - #lorem(10)
    - #lorem(10)
  ],
)

If you need your wrapper function to do more, use the show rule of grid.cell. For example, this show rule will insert a black-stroked rectangle at the top left of each cell:

#show grid.cell: it => block(inset: 10pt, {
  place(top+left, rect())
  it
})