[mem_cache] Drop the torch.unique sync from the SWA page expansion

[hnyls2002]

• Expand free_swa's whole-page coverage without torch.unique (its data-dependent output shape synchronizes the scheduler stream): keep the duplicate page entries and let the paged free's own page dedup collapse them. End state is unchanged; a debug_mode reference check compares against the unique-based page set on every real input.

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CI States

Latest PR Test (Base): 🚫 Run #33545635926
Latest PR Test (Extra): ❌ Run #33545635640
Latest PR Test (AMD ROCm 7.2): 🚫 Run #33545635902

[hnyls2002]

/tag-and-rerun-ci

[hnyls2002]

/rerun-test registered/unit/mem_cache/test_swa_unittest.py registered/unit/mem_cache/test_swa_eviction_boundary.py registered/radix_cache/test_swa_radix_cache_kl.py registered/radix_cache/unified_radix_tree/test_unified_radix_cache_kl_swa.py registered/sessions/test_streaming_session_swa.py registered/sessions/test_streaming_session_swa_extra.py registered/chunked_prefill/test_scripted_swa_1gpu.py

[github-actions]

Results for /rerun-test registered/unit/mem_cache/test_swa_unittest.py registered/unit/mem_cache/test_swa_eviction_boundary.py registered/radix_cache/test_swa_radix_cache_kl.py registered/radix_cache/unified_radix_tree/test_unified_radix_cache_kl_swa.py registered/sessions/test_streaming_session_swa.py registered/sessions/test_streaming_session_swa_extra.py registered/chunked_prefill/test_scripted_swa_1gpu.py:

🚀 1-gpu-h100 (6 tests): ✅ View workflow run

cd test/ && python3 registered/unit/mem_cache/test_swa_unittest.py
cd test/ && python3 registered/unit/mem_cache/test_swa_eviction_boundary.py
cd test/ && python3 registered/radix_cache/test_swa_radix_cache_kl.py
cd test/ && python3 registered/sessions/test_streaming_session_swa.py
cd test/ && python3 registered/sessions/test_streaming_session_swa_extra.py
cd test/ && python3 registered/chunked_prefill/test_scripted_swa_1gpu.py

🚀 2-gpu-h100 (1 test): ✅ View workflow run

cd test/ && python3 registered/radix_cache/unified_radix_tree/test_unified_radix_cache_kl_swa.py

[hnyls2002]

The commit containing this change passed all the basic CI: https://github.com/sgl-project/sglang/actions/runs/33547072775