[310B] Centralize remaining fallback ops in SoC policy

[lvyufeng]

Summary

• move the remaining 310B fallback-op set from ops_310b.py into ops_soc.py capability table (fallback_ops)
• keep ops_310b.py as a compatibility shim module
• make ops_soc.use_fallback prefer capability-table fallback set and retain legacy module fallback path for compatibility
• extend SoC policy unit tests to lock full 310B fallback-op set and capability behavior

Scope

• mechanism-only routing centralization
• no intended runtime behavior change

Validation

• env PYTHONPATH=src conda run -n mindtorch311 python -m pytest -q tests/mindtorch_v2/test_npu_soc_policy.py
• env PYTHONPATH=src conda run -n mindtorch311 python -m pytest -q tests/mindtorch_v2/contract/test_schema_registration_order.py
• env PYTHONPATH=src conda run -n mindtorch311 python -m pytest -q tests/mindtorch_v2/contract/test_schema_coverage.py
• env PYTHONPATH=src conda run -n mindtorch311 python -m pytest -q tests/mindtorch_v2/test_310b_watchlist_npu.py