Construct an ni_call: bind parameter values to a spec

Creates a validated call object that captures a spec plus concrete parameter values, ready for execution or dry-run preview.

Usage

ni_call(
  spec_id,
  ...,
  .cwd = NULL,
  .env = NULL,
  .engine = NULL,
  .profile = NULL,
  .validate = TRUE
)

spec_id: A spec ID (e.g. "fsl.bet"), path to a JSON file, or an ni_spec object.
...: Named parameter values.
.cwd: Working directory override.
.env: Named character vector of environment variables.
.engine: Execution engine override. One of "auto", "native", "docker", "apptainer".
.profile: Runtime profile override (maps to profiles entry in niflowr.yml).
.validate: Logical; validate inputs at construction time. Default TRUE.

An ni_call object (S3 list).