Point to router-slm-v2 successor

Update README.md

Update references for rename to router-slm

Update references for repository rename

Trim model card to usage documentation

Clarify version guidance: v40 final default, v33 benchmarked artifact

Add GRPO router model card

Adapter at policy v40 (checkpoint-0040, fullctx150 run complete)

Adapter at policy v33 (checkpoint-0033, fullctx150 run)

Adapter at policy v5 (checkpoint-0005, fullctx150 run)

Adapter at policy v3 (checkpoint-0003, fullctx150 run)

initial commit