[DO NOT MERGE] Temporarily force PR builds to validate 3.15 instead of 3.10

PR runs set LIMIT_PR_BUILDS, which trims the matrix to the oldest python
(3.10), so none of the 3.15 changes in this PR would be exercised by CI.
Force 3.15 where it exists in the channel's matrix; release (no 3.15) and
windows-arm64 (own pinned list) fall back to the previous behaviour.

Revert this commit before merging.

Author: atalman

tools/scripts/generate_binary_build_matrix.py

@@ -474,7 +474,16 @@ def generate_wheels_matrix(
             arches += [XPU]
 
     if limit_pr_builds:
-        python_versions = [python_versions[0]]
+        # ---------------------------------------------------------------
+        # [DO NOT MERGE] Temporary: PR builds normally validate only the
+        # OLDEST python (3.10), which would not exercise the 3.15 changes
+        # in this PR at all. Force 3.15 so CI actually covers them.
+        # Revert this hunk to `python_versions = [python_versions[0]]`
+        # before merging.
+        # ---------------------------------------------------------------
+        python_versions = (
+            ["3.15"] if "3.15" in python_versions else [python_versions[0]]
+        )
 
     global WHEEL_CONTAINER_IMAGES