Summary

This patch fixes the VMM handle lifecycle by moving cuMemRelease() calls inside the transaction boundary so release failures can still trigger rollback cleanup.

Changes

• In allocate(), create a rollback-aware release closure and perform cuMemRelease(handle) before trans.commit(); callback is conditional to avoid double release.
• In _grow_allocation_fast_path(), release new_handle before trans.commit() and guard rollback callback to only release if not already released.
• In _grow_allocation_slow_path(), keep old_handle pinned until remap-dependent rollback logic is done, then release both new_handle and old_handle before trans.commit() through guarded callbacks.
• Add regression tests that force cuMemRelease() failures for allocate/fast/slow paths and assert rollback cleanup callbacks still execute.

Validation

I attempted to run the targeted pytest selection in this environment, but pytest is not installed in the available interpreter.

Notes

This preserves rollback behavior while addressing the failure-after-commit edge described in PR review (release failures now remain within rollback coverage).