ci: Add dependabot for requirements

.github/dependabot.yml

@@ -0,0 +1,17 @@
+version: 2
+updates:
+  - package-ecosystem: "pip"
+    directory: "/requirements"
+    schedule:
+      interval: "daily"
+    open-pull-requests-limit: 10
+    labels:
+      - "dependencies"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    open-pull-requests-limit: 10
+    labels:
+      - "dependencies"

.github/workflows/ci.yml

@@ -45,10 +45,7 @@ jobs:
 
       - name: Install dependencies
         run: |
-          pip install numpy
-          pip install ml_dtypes
-          pip install pytest
-          pip install torch --index-url https://download.pytorch.org/whl/cpu
+          pip install -r requirements/ci.txt --index-url https://download.pytorch.org/whl/cpu
 
       - name: Build nanobind extension
         run: pip install .
@@ -103,10 +100,7 @@ jobs:
 
       - name: Install dependencies
         run: |
-          pip install numpy
-          pip install ml_dtypes
-          pip install pytest
-          pip install torch --index-url https://download.pytorch.org/whl/cpu
+          pip install -r requirements/ci.txt --index-url https://download.pytorch.org/whl/cpu
 
       - name: Build nanobind extension
         run: pip install .

requirements/ci.txt

@@ -0,0 +1,6 @@
+# CI Python dependencies for simpler.
+# Keep upper bounds here; Dependabot updates this file.
+numpy<=2.0.2
+ml_dtypes<=0.5.1
+pytest<=8.3.5
+torch<=2.6.0