Try seqkit sliding, e.g.,

$ echo -ne ">seq\nACTGGTCA\n" | seqkit sliding -s 3 -W 4 -g
>seq_sliding:1-4
ACTG
>seq_sliding:4-7
GGTC
>seq_sliding:7-8
CA

For you, you need set the windows size as 10,000 with a step of 9900

seqkit sliding -s 9900  -W 10000 genome.fa.gz -o genome.s.fa.gz

And you can further split the output into files with single sequence.

seqkit sliding -s 9900  -W 10000 genome.fa.gz  | seqkit split2 -s 1 -O outdir