[RELEASE ONLY CHANGES] Fix Python 3.14 wheel dependency setup (#21584)

Release-only change. Do not merge to main.

Python 3.14 macOS and Windows wheel builds fail during dependency setup
because the pinned torchtune revision requires `pyarrow<21`. PyArrow
releases before 21 do not provide Python 3.14 wheels, so pip attempts an
unsupported source build.

Keep the existing example dependency installation because wheel smoke
tests export MobileNetV3 through torchvision. Skip only torchtune on
Python 3.14; it is not used by wheel construction or the wheel smoke
tests. Python 3.10-3.13 and the normal Llama setup continue to install
torchtune.

Also add `requirements-examples.txt` to the wheel workflow path filters
because the pre-build script consumes it.

Failed post-merge jobs:
- macOS:
https://github.com/pytorch/executorch/actions/runs/30957868484/job/92155043950
- Windows:
https://github.com/pytorch/executorch/actions/runs/30957868415/job/92155038157

Test plan:
- `bash -n .ci/scripts/wheel/pre_build_script.sh
install_requirements.sh`
- Parsed all four modified workflow YAML files
- Verified the torchtune environment marker selects Python 3.10-3.13 and
excludes Python 3.14
- `git diff --check`
- Full Python 3.10-3.14 Linux, AArch64, macOS, and Windows wheel
matrices delegated to CI.

Authored with Codex.

Author: JacobSzwejbka

.github/workflows/build-wheels-aarch64-linux.yml

@@ -8,6 +8,7 @@ on:
       - .github/workflows/build-wheels-aarch64-linux.yml
       - examples/**/*
       - pyproject.toml
+      - requirements-examples.txt
       - setup.py
   push:
     branches:

.github/workflows/build-wheels-linux.yml

@@ -8,6 +8,7 @@ on:
       - .github/workflows/build-wheels-linux.yml
       - examples/**/*
       - pyproject.toml
+      - requirements-examples.txt
       - setup.py
   push:
     branches:

.github/workflows/build-wheels-macos.yml

@@ -8,6 +8,7 @@ on:
       - .github/workflows/build-wheels-macos.yml
       - examples/**/*
       - pyproject.toml
+      - requirements-examples.txt
       - setup.py
   push:
     branches:

.github/workflows/build-wheels-windows.yml

@@ -7,6 +7,7 @@ on:
       - .github/workflows/build-wheels-windows.yml
       - examples/**/*
       - pyproject.toml
+      - requirements-examples.txt
       - setup.py
   push:
     branches:

requirements-examples.txt

@@ -3,5 +3,5 @@
 datasets == 3.6.0 # 4.0.0 deprecates trust_remote_code and load scripts. For now pin to 3.6.0
 timm == 1.0.7
 torchsr == 1.0.4
-torchtune @ git+https://github.com/pytorch/torchtune.git@3c1872ace149f03ef4ffec765d3f0a5fd0399497
+torchtune @ git+https://github.com/pytorch/torchtune.git@3c1872ace149f03ef4ffec765d3f0a5fd0399497 ; python_version < "3.14"
 transformers == 5.0.0rc1