Arm backend: requirements-arm-tosa.txt is uninstallable on Python 3.13/3.14 although pyproject.toml declares support up to <3.15

🐛 Describe the bug

Environment

• macOS 26.5 (Apple Silicon), Python 3.14.6
• executorch main @ d614f9dba4

Repro

Install executorch on Python 3.14 (allowed by pyproject.toml: requires-python = ">=3.10,<3.15" — the install works), then run the Arm setup:

./examples/arm/setup.sh --i-agree-to-the-contained-eula

It fails installing backends/arm/requirements-arm-tosa.txt:

ERROR: Ignored the following versions that require a different python version:
  0.0.1 Requires-Python >=3.10,<3.13; 0.1.0 Requires-Python >=3.10,<3.13
ERROR: Could not find a version that satisfies the requirement tosa-adapter-model-explorer==0.1.0 (from versions: none)

Root cause

tosa-adapter-model-explorer publishes only for Python <3.13, but it is pinned unconditionally in backends/arm/requirements-arm-tosa.txt — whose own header comment says "These dependencies need to match pyproject.toml". The two version envelopes contradict each other, so the effective supported range for the Arm flow is <3.13, which users only discover mid-setup.

Suggested fix

One of:

1. Publish tosa-adapter-model-explorer wheels for 3.13/3.14 (it's an Arm-maintained package), or
2. Make it an environment-conditional dependency (; python_version < "3.13") — it's a Model Explorer visualization adapter, not needed for the core AOT flow, or
3. Lower requires-python (or document the Arm backend's narrower envelope) so the failure happens at install time with a clear message instead of mid-setup.

Everything worked after rebuilding the venv on Python 3.12.

Versions

PyTorch version: 2.13.0
Is debug build: False
CUDA used to build PyTorch: None
ROCM used to build PyTorch: N/A

OS: macOS 26.5.2 (arm64)
GCC version: Could not collect
Clang version: 21.0.0 (clang-2100.1.1.101)
CMake version: version 3.31.10
Libc version: N/A

Python version: 3.12.14 (main, Aug 12 2026, 13:57:54) [Clang 21.0.0 (clang-2100.1.1.101)] (64-bit runtime)
Python platform: macOS-26.5.2-arm64-arm-64bit
Is CUDA available: False
CUDA runtime version: No CUDA
CUDA_MODULE_LOADING set to: N/A
GPU models and configuration: No CUDA
Nvidia driver version: No CUDA
cuDNN version: No CUDA
Is XPU available: False
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: False
Caching allocator config: N/A

CPU:
Apple M4 Pro

Versions of relevant libraries:
[pip3] executorch==1.5.0+d614f9d
[pip3] numpy==2.5.2
[pip3] pytorch_tokenizers==1.3.0
[pip3] torch==2.13.0
[pip3] torchao==0.18.0.dev20260729+cpu
[pip3] torchaudio==2.11.0
[pip3] torchdata==0.11.0+cpu
[pip3] torchsr==1.0.4
[pip3] torchtune==0.0.0
[pip3] torchvision==0.28.0
[conda] Could not collect

cc @larryliu0820 @GregoryComer @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @Sebastian-Larsson @robell @rascani