Document UV auto-detection and update to Python 3.14

- Removed obsolete MXENV_UV_GLOBAL from all preseed examples
- Added UV Package Installer sections explaining auto-detection
- Documented new UV_PYTHON setting with version spec examples
- Added warnings that UV_PYTHON defaulting to PRIMARY_PYTHON is
  backward compatibility only and should be explicitly set
- Updated all examples to use Python 3.14 (3.13 for Plone)
- All preseed examples now explicitly set UV_PYTHON

Author: jensens

docs/source/getting-started.md

@@ -63,6 +63,23 @@ For details read the chapter [on topics and it's domains](topics-and-domains).
 Do not add custom settings to settings section.
 They will be lost on next `mxmake init` respective `mxmake update` run.
 
+### Python Package Installer
+
+By default, mxmake uses `pip` as the package installer. You can switch to [UV](https://docs.astral.sh/uv/) by setting `PYTHON_PACKAGE_INSTALLER=uv` in the settings section.
+
+When using UV, mxmake automatically detects if UV is installed globally or installs it locally in the virtual environment.
+
+```{note}
+When using UV, you should explicitly set `UV_PYTHON` to specify which Python version UV should use. While `UV_PYTHON` currently defaults to `PRIMARY_PYTHON` for backward compatibility, this default may change in future versions. Set `UV_PYTHON` explicitly to avoid surprises.
+```
+
+Example:
+```makefile
+PRIMARY_PYTHON?=python3
+PYTHON_PACKAGE_INSTALLER?=uv
+UV_PYTHON?=3.14
+```
+
 ## How to use on the Windows operating system
 
 mxmake works excellent on Windows!

docs/source/preseeds.md

@@ -15,9 +15,10 @@ topics:
   core:
     # include domain mxenv
     mxenv:
-      # set PYTHON_MIN_VERSION and PYTHON_PACKAGE_INSTALLER
-      PYTHON_MIN_VERSION: 3.10
+      # set PYTHON_MIN_VERSION, PYTHON_PACKAGE_INSTALLER and UV_PYTHON
+      PYTHON_MIN_VERSION: 3.14
       PYTHON_PACKAGE_INSTALLER: uv
+      UV_PYTHON: "3.14"
   qa:
     # include domains from qa topic but do not override default settings
     ruff:
@@ -36,6 +37,26 @@ Now initialize the project with the preseeds:
 $ mxmake init -p preseeds.yaml
 ```
 
+## UV Package Installer
+
+When `PYTHON_PACKAGE_INSTALLER` is set to `uv`, mxmake automatically detects whether UV is installed globally on your system.
+
+```{important}
+When using UV, you should explicitly set `UV_PYTHON` to specify which Python version UV should use. While `UV_PYTHON` currently defaults to `PRIMARY_PYTHON` for backward compatibility, relying on this default is not recommended and may change in future versions.
+```
+
+The `UV_PYTHON` setting accepts version specs like `3.13`, `3.14`, or `[email protected]`:
+
+```yaml
+topics:
+  core:
+    mxenv:
+      PYTHON_MIN_VERSION: "3.14"
+      PRIMARY_PYTHON: python3
+      PYTHON_PACKAGE_INSTALLER: uv
+      UV_PYTHON: "3.14"  # Explicitly specify Python version for UV
+```
+
 ## Examples
 
 ### Create a simple Python project
@@ -56,8 +77,9 @@ Enter the `hello-world-` directory and create a file `preseed.yaml`:
 topics:
   core:
     mxenv:
-      PYTHON_MIN_VERSION: "3.10"
+      PYTHON_MIN_VERSION: "3.14"
       PYTHON_PACKAGE_INSTALLER: uv
+      UV_PYTHON: "3.14"
     sources:
   qa:
     ruff
@@ -102,8 +124,9 @@ topics:
     base:
       RUN_TARGET: zope-start
     mxenv:
-      PYTHON_MIN_VERSION: "3.10"
+      PYTHON_MIN_VERSION: "3.13"
       PYTHON_PACKAGE_INSTALLER: uv
+      UV_PYTHON: "3.13"
   applications:
     zope:
     plone: