get_task_info hardcodes commit to NA, so every task_info.json reports a null commit

[rcannood]

task_info.json always comes out with "commit": null, for every task, because
get_task_info hardcodes it:

openproblems/src/reporting/get_task_info/script.R

Line 45 in 9fe740d

commit = jsonlite::unbox(NA_character_), # TODO: Add when available in task_info.yaml

commit = jsonlite::unbox(NA_character_), # TODO: Add when available in task_info.yaml

From a report I rendered yesterday (task_spatial_simulators, run
run_2026-07-29_13-06-59):

{
  "name": "spatial_simulators",
  "commit": null,
  "label": "Spatial Simulators",
  ...
  "version": "build_main",

version is the revision (build_main), so as it stands there is nothing in the
published results that pins a task to the code that produced it. Methods and
datasets both already carry one:

# get_method_info/script.R
commit = jsonlite::unbox(.config$build_info$git_commit %||% "missing-sha"),

# get_dataset_info/script.R
commit = jsonlite::unbox(.dataset$dataset_commit %||% "missing-sha"),

Proposal

The TODO's precondition is easy to satisfy on the task side -- workflow.commitId
is available in run_benchmark, so the task can write the commit into
task_info.yaml alongside everything else it already copies out of _viash.yaml.
I have done that in task_spatial_simulators
(openproblems-bio/task_spatial_simulators#33) and am happy to send the same change
to task_template.

That leaves this side, which would become:

commit = jsonlite::unbox(task_info_yaml$commit %||% "missing-sha"),

matching what get_method_info does, so a task whose workflow predates the change
degrades to "missing-sha" rather than breaking.

[rcannood]

Let's go with commit, and no "missing-sha" fallback. A
task whose results predate this should show up as a null rather than a plausible
looking placeholder -- that is the results generator's problem to fix, and hiding it
behind a string only makes it harder to spot.

One wrinkle though. jsonlite::unbox() does not error on a NULL, it serialises it
as {}:

task_info_yaml <- list(name = "task_x")   # no commit field, i.e. every task today

jsonlite::toJSON(
  list(
    name = jsonlite::unbox("task_x"),
    commit = jsonlite::unbox(task_info_yaml$commit)
  ),
  pretty = TRUE
)
#> {
#>   "name": "task_x",
#>   "commit": {}
#> }

So the bare version gives an empty object where we want a null. Keeping the %||%
purely to land on NA_character_ does the trick:

commit = jsonlite::unbox(task_info_yaml$commit %||% NA_character_),

#> {
#>   "name": "task_x",
#>   "commit": null
#> }

which is also what the hardcoded line emits today, so nothing downstream sees a new
shape until a task actually starts writing the field.