feat(runtime): Add offset device copy wrapper

[high-cloud]

Summary

• Add DistributedWorker.copy_to_offset for H2D copies into an offset of a live device allocation.
• Forward the allocation base and byte offset separately to the simpler orchestrator.
• Document the helper on DistributedWorker and cover its argument forwarding with a unit test.

Motivation

Simpler validates device-pointer provenance and rejects interior pointers passed through copy_to.
Callers updating a slice of a persistent allocation therefore need an explicit base-plus-offset API.
This wrapper exposes that API to PyPTO and unblocks offset cache-page updates in serving workloads.

Dependency

• Depends on hw-native-sys/simpler#1538.
• Merge the simpler PR before this wrapper PR.

Validation

• cmake --build build --parallel
• python -m pytest tests/ut/runtime/test_distributed_worker.py -n auto --maxprocesses 8 -q: 104 passed
• PyPTO pre-commit checks on the changed files: passed, including Ruff and Pyright
• Full unit-suite attempt: 7772 passed, 2 skipped; 11 failures and 4 setup errors were caused by the locally installed _task_interface predating the simpler source-tree build stamp

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[high-cloud]

Closing as superseded by the revised simpler #1538, which fixes range validation in the existing copy_to() API. PyPTO no longer needs a copy_to_offset wrapper or public API expansion.