Update Python version requirements and installation instructions

docs/changelog.md

@@ -13,6 +13,9 @@ behavior they verify rather than listed separately.
 
 ### Added
 
+- Install the legacy Kwik GUI dependencies with the optional `phy[kwik]`
+  extra. The supported legacy environment uses Python 3.10 or 3.11 and NumPy
+  1.23 without constraining regular Template GUI installations.
 - Select the first eligible clusters in the Similarity View with
   `Control+Space`. The default is 15 clusters; **Select > Select N Similar**
   changes the number and remembers it across sessions.

docs/installation.md

@@ -161,14 +161,17 @@ phy template-gui /path/to/output/params.py
 ## Legacy Kwik support
 
 The Template GUI is the recommended workflow for current template-based sorters.
-The legacy Kwik GUI needs additional packages. Install them in a separate
-uv-managed environment because `klustakwik2` needs NumPy, setuptools, and Cython
-available while it builds:
+The legacy Kwik GUI requires Python 3.10 or 3.11 because its unmaintained
+dependencies are not compatible with current NumPy releases. Install it in a
+separate uv-managed environment. The `kwik` extra supplies the tested legacy
+dependency versions, while `klustakwik2` still needs NumPy, setuptools, and
+Cython available while it builds:
 
 ```bash
-uv venv --python 3.12 phy-kwik-env
-uv pip install --python phy-kwik-env phy klusta cython
+uv venv --python 3.11 phy-kwik-env
+uv pip install --python phy-kwik-env "numpy>=1.23,<1.24" "setuptools<81" six cython
 uv pip install --python phy-kwik-env --no-build-isolation klustakwik2
+uv pip install --python phy-kwik-env "phy[kwik]"
 ```
 
 Activate the environment using the command printed by `uv venv`. It can then be

pyproject.toml

@@ -22,6 +22,7 @@ classifiers = [
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
 ]
 requires-python = ">=3.10"
 
@@ -34,7 +35,7 @@ dependencies = [
     "joblib",
     "matplotlib",
     "mtscomp",
-    "numpy",
+    "numpy>=1.23",
     "pillow",
     "pip",
     "PyQt5>=5.15.11,<5.16",
@@ -55,6 +56,13 @@ Repository = "https://github.com/cortex-lab/phy"
 Documentation = "https://phy.readthedocs.io/en/latest/"
 
 [project.optional-dependencies]
+kwik = [
+    "klusta",
+    "klustakwik2",
+    "numpy>=1.23,<1.24",
+    "setuptools<81",
+    "six",
+]
 dev = [
     "Cython>=3.0",
     "pytest",
@@ -108,6 +116,12 @@ phy = [
 
 [tool.uv]
 required-version = ">=0.11.8,<0.13"
+conflicts = [
+    [
+        { extra = "kwik" },
+        { group = "dev" },
+    ],
+]
 required-environments = [
     "sys_platform == 'win32' and platform_machine == 'AMD64'",
 ]