.tool-versions(python) Default to Python 3.15

why: CPython 3.15.0 was released 2026-10-09, past the 3-day cooldown.
mise resolves `3.15` to the newest installed 3.15.x, so the pin needs
no patch bumps. mise now defaults to Python 3.15 here.

See also:
- https://www.python.org/downloads/release/python-3150/
- https://docs.python.org/3.15/whatsnew/3.15.html

Author: tony

.tool-versions

@@ -1,3 +1,3 @@
 just 1.58.0
 uv 0.13.1
-python 3.14 3.13 3.12 3.11 3.10
+python 3.15 3.14 3.13 3.12 3.11 3.10