Pin requires-python in poetry test project to match the conda env

Poetry's resolver was rejecting torchvision 0.27.0 because the
project's open-ended `requires-python = ">=3.11"` (generated by
`poetry new`) had to be satisfied across every Python in that range,
and torchvision 0.27.0 excludes Python 3.14.1 specifically:

  - torchvision requires Python !=3.14.1,>=3.10
  - test-poetry requires Python >=3.11
  - 3.14.1 is in the project range but excluded by torchvision
  - therefore no version of torchvision can be locked

This was only visible after dropping `--quiet` in the prior commit.
Narrow the project's requires-python to ">=3.11,<3.12" (or whatever
MATRIX_PYTHON_VERSION resolves to), which both unblocks resolution
and makes the test reflect the actual runtime we set up in conda.

Authored with Claude Code.

Author: atalman

.github/scripts/validate_poetry.sh

@@ -12,6 +12,18 @@ poetry --version
 poetry new test_poetry
 cd test_poetry
 
+# `poetry new` emits an open-ended requires-python = ">=X.Y", which causes
+# resolution to fail whenever a target wheel excludes a future Python that
+# falls inside that range (e.g. torchvision 0.27.0 excludes Python 3.14.1,
+# so Poetry refuses to lock it across ">=3.11"). Pin the range to the conda
+# env's exact Python minor so resolution matches the runtime we actually
+# test against.
+PY_MAJOR="${MATRIX_PYTHON_VERSION%.*}"
+PY_MINOR="${MATRIX_PYTHON_VERSION#*.}"
+PY_NEXT_MINOR=$((PY_MINOR + 1))
+sed -i -E "s|^requires-python\\s*=.*|requires-python = \">=${MATRIX_PYTHON_VERSION},<${PY_MAJOR}.${PY_NEXT_MINOR}\"|" pyproject.toml
+sed -i -E "s|^python\\s*=\\s*\".*\"|python = \">=${MATRIX_PYTHON_VERSION},<${PY_MAJOR}.${PY_NEXT_MINOR}\"|" pyproject.toml
+
 TEST_SUFFIX=""
 if [[ ${TORCH_ONLY} == 'true' ]]; then
     TEST_SUFFIX=" --package torchonly"