[Bug] subgroup.py __all__ missing broadcast, group_size, invocation_id

[alanray-tech]

Summary

broadcast, group_size, and invocation_id are defined as public functions in python/quadrants/lang/simt/subgroup.py but are missing from the module's __all__ list.

Details

The __all__ list at the bottom of subgroup.py (line 172-200) includes all other public functions -- including TODO stubs like broadcast_first, all_true, any_true, all_equal, and shuffle_xor -- but omits these three working implementations:

• broadcast(value, index) (line 41) -- implemented, verified on CUDA/AMDGPU/SPIR-V
• group_size() (line 45) -- implemented, SPIR-V only
• invocation_id() (line 49) -- implemented, verified on CUDA/AMDGPU/SPIR-V

Impact

from quadrants.lang.simt.subgroup import * will not import these three functions. They remain accessible via explicit import or via qd.simt.subgroup.broadcast(), so impact is low, but it is inconsistent.

Suggested fix

Add the three missing names to __all__:

__all__ = [
    "barrier",
    "memory_barrier",
    "elect",
    "all_true",
    "any_true",
    "all_equal",
    "broadcast",        # <-- add
    "broadcast_first",
    "group_size",       # <-- add
    "invocation_id",    # <-- add
    "reduce_add",
    ...
]

Found during

Review of #639 (docs for qd.simt.subgroup).