docs: Add godoc comments to methods for capturing log message output(s)

tfexec/cmd.go

diff --git a/tfexec/cmd.go b/tfexec/cmd.go
index a5f17cb..153667a 100644
--- a/tfexec/cmd.go
+++ b/tfexec/cmd.go
@@ -210,6 +210,8 @@
 	return cmd
 }
 
+// runTerraformCmdJSON runs a given command that produces a single, static JSON output.
+// This is decoded into the provided v argument.
 func (tf *Terraform) runTerraformCmdJSON(ctx context.Context, cmd *exec.Cmd, v interface{}) error {
 	var outbuf = bytes.Buffer{}
 	cmd.Stdout = mergeWriters(cmd.Stdout, &outbuf)
@@ -224,6 +226,8 @@
 	return dec.Decode(v)
 }
 
+// runTerraformCmdJSONLog runs a given command that produces multiple, structured JSON log messages.
+// Due to this it returns an iterator that allows calling code to consume a stream of messages.
 func (tf *Terraform) runTerraformCmdJSONLog(ctx context.Context, cmd *exec.Cmd) iter.Seq[NextMessage] {
 	pr, pw := io.Pipe()
 	tf.SetStdout(pw)