Refactor: L3 SceneTestCase — HostCallable as Python DAG

[hw-native-sys-bot]

Summary

• Extend SceneTestCase to support L3 distributed tests (multi-chip + SubWorker)
• L3 CALLABLE structure mirrors L2: orchestration is a Python DAG function, callables is a mixed list of ChipCallable entries (compiled like L2) and SubCallable entries (registered as callable_id)
• Add CallableNamespace for orch functions to access compiled callables by name with dot-access, with keep() for lifetime management past drain()
• Extract _compile_chip_callable_from_spec helper reused by both L2 and L3 paths
• Rewrite test_l3_dependency.py and test_l3_group.py as SceneTestCase subclasses with module-level orch + sub functions
• Update conftest.py L3 fixture to register SubCallable entries and read device_count/num_sub_workers from case config dict

Test plan

• pip install . builds successfully
• pytest tests/ut -x -q — 149 passed
• L2 regression: pytest examples/.../test_vector_example.py --platform a2a3sim — PASSED
• L3 manual test: Python direct execution of full L3 flow — f[0]=47.0 (correct)
• CI: L3 sim tests via pytest

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request introduces support for Level 3 (L3) scene tests, enabling orchestration via Python DAG functions. Key additions include the CallableNamespace for dot-access to callables and lifetime management, refactored path resolution and compilation logic to support multiple callables, and updated test runners to handle L3 worker initialization. Feedback addresses a potential name collision in the standalone runner's shared sub_ids dictionary, risks of attribute overwriting in CallableNamespace due to direct dict updates, and a potential IndexError in the keep method when invoked without arguments.