Now, the shell completion -t(e.g. zsh) is as following:

❯ rg -t<Tab>
file type
agda          cabal         csv           fidl          hbs           license       minified      po            robot         sv            typoscript    z
...

In the code, it truncate :* of the output of rg --type-list

❯ rg --type-list|head -n1
agda: *.agda, *.lagda

How about adding the extension information? Like this:

❯ rg -t<Tab>
file type
agda     *.agda,*.lagda
aidl     *.aidl
...

It should can be realized, because zsh use (agda aidl) to provide the completion without prompt information, and use (agda\:*.agda,*.lagda aidl\:*.aidl) to provide the completion with prompt information.