Critical bug: all previous CCCL-ported changes to paged_attn.py were
applied to the root copy, but Dockerfile COPYs qwen3_6_scripts/ and
patch_ops.sh runs cp ./paged_attn.py from inside that directory.
Root paged_attn.py (630 lines) != qwen3_6_scripts/paged_attn.py (547 lines)
Now synced: both are 630 lines with CCCL-ported adaptive tile sizing.