Cannot run native python binary script without C++ toolchain

# 🐞 bug report

### Affected Rule

`py_binary`

### Is this a regression?

Not tested, unlikely.

### Description

A trivial pure-Python `py_binary` appears to require C++ toolchain resolution even though it does not produce any C++ compile or link actions.

In a minimal example, `bazel cquery //:hello_world --toolchain_resolution_debug='.*'` shows that Bazel resolves both:
- `@@bazel_tools//tools/python:toolchain_type`
- `@@bazel_tools//tools/cpp:toolchain_type`

However, `bazel aquery //:hello_world` only shows Python-related actions such as Python bytecode precompilation and bootstrap/template generation. There are no C++ compile or link actions for the target.

This is surprising for Python-only projects. In environments where no C++ toolchain is configured or available, this can cause a trivial `py_binary` to fail analysis even though the target itself does not build native code.

From a user perspective, I would expect a pure `py_binary` with no native extensions and no C/C++ deps to avoid requiring successful C++ toolchain resolution, or at least for the requirement to be documented if it is intentional.

## 🔬 Minimal Reproduction

`MODULE.bazel`
```starlark
module(
name = "bazel_hello_py",
version = "0.1.0",
)

bazel_dep(name = "rules_shell", version = "0.6.1")
bazel_dep(name = "rules_python", version = "1.7.0")
```
`BUILD.bazel`

```starlark
load("@rules_python//python:defs.bzl", "py_binary")

py_binary(
name = "hello_world",
srcs = ["hello_world.py"],
)
```

`hello_world.py`

```python
print("hello world")
```

```starlark
bazel run //:hello_world --repo_env=BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=<0|1>
bazel cquery //:hello_world --toolchain_resolution_debug='.*'
bazel aquery //:hello_world
```

Observed behavior:

1. `bazel run //:hello_world` succeeds if the `repo_env` is set to `0` but fails on `1`
2. `cquery shows that @@bazel_tools//tools/cpp:toolchain_type` is resolved for the target.
3. `aquery` shows only Python-related actions and no C++ compile/link actions.

This suggests the C++ toolchain resolution is happening even for a pure-Python binary with no actual C++ build work.

## 🔥 Exception or Error

```bash
$ bazel run //:hello_world --repo_env=BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1
ERROR: .../external/bazel_tools/src/tools/launcher/BUILD:75:10: While resolving toolchains for target @@bazel_tools//src/tools/launcher:launcher_maker (04bf134): No matching toolchains found for types:
@@bazel_tools//tools/cpp:toolchain_type
To debug, rerun with --toolchain_resolution_debug='@@bazel_tools//tools/cpp:toolchain_type'
For more information on platforms or toolchains see https://bazel.build/concepts/platforms-intro.
ERROR: Analysis of target '//:hello_world' failed; build aborted: Analysis failed
INFO: Elapsed time: 0.107s, Critical Path: 0.01s
INFO: 1 process: 1 internal.
ERROR: Build did NOT complete successfully
ERROR: Build failed. Not running target
```

## 🌍 Your Environment

**Operating System:**

  

     Linux (Ubuntu LTS 24.04)

  

**Output of `bazel version`:**

  

    Bazelisk version: v1.29.0 Build label: 9.2.0 Build target: @@//src/main/java/com/google/devtools/build/lib/bazel:BazelServer Build time: Mon Jul 13 18:15:04 2026 (1783966504) Build timestamp: 1783966504 Build timestamp as int: 1783966504

  

**Rules_python version:**

  

     1.7.0

  

**Anything else relevant?**

Related issues I found while searching:
rules_python #1857 discusses py_binary and C++ toolchain resolution in cross-compilation scenarios.
rules_python #2500 discusses replacing the stage1 bootstrap with a native launcher.

My main question is whether this C++ toolchain resolution for a pure py_binary is intentional.

Bắt đầu với ví dụ MODULE.bazel và BUILD.bazel tối thiểu, sau đó chạy các lệnh bazel run, cquery và aquery đã được báo cáo với BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN được đặt thành 1. So sánh các toolchain và action đã được phân giải để xác định liệu một py_binary thuần có thể tránh việc phân giải C++ toolchain hay không; hoàn tất khi hành vi này được sửa hoặc yêu cầu có chủ đích của nó được ghi lại.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.