feat: add remote dispatch plan evidence

[hyeokjun32]

Summary

• Added worker selection evidence to remote dispatch results.
• Added retry/fallback planning and plan-only remote execution metadata without opening network connections.
• Updated README and remote dispatch docs to keep the production remote execution boundary explicit.

Validation

• PYTHONDONTWRITEBYTECODE=1 .venv/bin/python -m pytest tests/test_remote_dispatch.py -q -p no:cacheprovider
• PYTHONDONTWRITEBYTECODE=1 .venv/bin/python -m pytest -q -p no:cacheprovider
• PYTHONPATH=src PYTHONDONTWRITEBYTECODE=1 .venv/bin/python -m inferedge_orchestrator remote-dispatch --registry examples/remote_worker_registry.json --request examples/remote_task_request.json --output /tmp/inferedge_remote_dispatch_plan.json
• git diff --check

Notes

• This is still a file-based/plan-only remote operation starter.
• No SSH/HTTP network execution or production remote worker behavior is claimed.