Require user plan() for parallel=TRUE; fix as_wt_nwt false-positive warnings

- parallel = TRUE now errors with a cli-styled message if no non-sequential
  future::plan() is active; users must call e.g. future::plan(future::multisession)
  before using parallel = TRUE (breaking change)
- Removed auto-setup/teardown of multisession plan inside as.sir(), which was
  slow and caused version-mismatch issues with load_all() workflows
- Added as_wt_nwt to the exclusion list in as_sir_method() to suppress
  false-positive "no longer used" warnings during parallel runs
- Fixed pieces_per_col row-batch calculation to use n_workers (total available
  workers from the active plan) instead of n_cores (workers clipped to n_cols),
  so row-batch mode activates correctly when n_cols < n_workers
- Updated @param parallel and @param max_cores roxygen docs; regenerated man/as.sir.Rd
- Updated sequential-mode hint to instruct users to set plan() first

https://claude.ai/code/session_01M1Jvf2Miu6JL4TQrEh1wS8

man/as.sir.Rd

@@ -150,9 +150,9 @@ The default \code{"conservative"} setting ensures cautious handling of uncertain
 
 \item{col_mo}{Column name of the names or codes of the microorganisms (see \code{\link[=as.mo]{as.mo()}}) - the default is the first column of class \code{\link{mo}}. Values will be coerced using \code{\link[=as.mo]{as.mo()}}.}
 
-\item{parallel}{A \link{logical} to indicate if parallel computing must be used, defaults to \code{FALSE}. Requires the \code{\link[future.apply:future_lapply]{future.apply}} package. If a non-sequential \code{\link[future:plan]{future::plan()}} is already active (e.g., set by the user via \code{future::plan(future::multisession)}), that plan is respected and left unchanged after the call. Otherwise, a temporary \code{multisession} plan is set automatically and torn down on exit. Parallelism distributes columns across workers; it is most beneficial when there are many antibiotic columns and a large number of rows.}
+\item{parallel}{A \link{logical} to indicate if parallel computing must be used, defaults to \code{FALSE}. Requires the \code{\link[future.apply:future_lapply]{future.apply}} package. \strong{A non-sequential \code{\link[future:plan]{future::plan()}} must already be active before setting \code{parallel = TRUE}} — for example, \code{future::plan(future::multisession)}. An error is thrown if \code{parallel = TRUE} is used without a plan set by the user. Parallelism distributes columns (and optionally row batches) across workers; it is most beneficial when there are many antibiotic columns and a large number of rows.}
 
-\item{max_cores}{Maximum number of workers to use if \code{parallel = TRUE} and no \code{\link[future:plan]{future::plan()}} has been set by the user. Use a negative value to subtract that number from the available number of cores, e.g. a value of \code{-2} on an 8-core machine means at most 6 workers will be used. Defaults to \code{-1}. There will never be used more workers than variables to analyse. The number of available cores is detected using \code{\link[parallelly:availableCores]{parallelly::availableCores()}} if that package is installed, and base \R's \code{\link[parallel:detectCores]{parallel::detectCores()}} otherwise. This argument is ignored when the user has already set a \code{\link[future:plan]{future::plan()}}.}
+\item{max_cores}{Maximum number of workers to use when \code{parallel = TRUE}. Use a negative value to subtract that number from the available workers, e.g. a value of \code{-2} means at most \code{nbrOfWorkers() - 2} workers will be used. Defaults to \code{-1} (all but one worker). There will never be more workers used than there are antibiotic columns to analyse.}
 
 \item{clean}{A \link{logical} to indicate whether previously stored results should be forgotten after returning the 'logbook' with results.}
 }