yaml-writing `brief` field in validation steps

I'm unsure whether this used to be supported at all (at least not for the past 2 minor versions), but it seems that brief is not preserved when writing to yaml, unlike e.g., label:

agent <- create_agent(~ small_table) |> 
  col_vals_lt(c(a, c), 5, label = "a label", brief = "a brief")

yaml_agent_string(agent, expanded = FALSE)
#> type: agent
#> tbl: ~small_table
#> tbl_name: ~small_table
#> label: '[2025-01-23|16:02:21]'
#> lang: en
#> locale: en
#> steps:
#> - col_vals_lt:
#>     columns: c(a, c)
#>     value: 5.0
#>     label: a label

yaml_agent_string(agent, expanded = TRUE)
#> type: agent
#> tbl: ~small_table
#> tbl_name: ~small_table
#> label: '[2025-01-23|16:02:21]'
#> lang: en
#> locale: en
#> steps:
#> - col_vals_lt:
#>     columns: c("a")
#>     value: 5.0
#>     label: a label
#> - col_vals_lt:
#>     columns: c("c")
#>     value: 5.0
#>     label: a label

A principled approach to this would seem to also require #273, such that auto-generated briefs can skip being written out.

I'm also surprised that this issue hasn't seen a ticket yet - perhaps not many folks are in the business of customizing and recording briefs? @rich-iannone do you have any thoughts on the status of brief? I'm trying to weigh the pros of adding this feature against the cons of maintenance burden that it might come with :)