Hash-pin action usages, minimize CI/CD permissions (#309)

Signed-off-by: William Woodruff <william@yossarian.net>

Author: woodruffw

.github/dependabot.yml

@@ -0,0 +1,12 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    cooldown:
+      default-days: 7
+    directory: /
+    schedule:
+      interval: weekly
+    groups:
+      github-actions:
+        patterns:
+          - "*"

.github/workflows/build.yml

@@ -12,13 +12,16 @@ env:
   PIP_VERBOSE: true
   PYMSBUILD_VERBOSE: true
 
+permissions: {}
 
 jobs:
   build:
     runs-on: windows-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+      with:
+        persist-credentials: false
 
     - name: 'Remove existing PyManager install'
       run: |
@@ -38,7 +41,7 @@ jobs:
     # We move faster than GitHub's Python runtimes, so use NuGet instead
     # One day we can use ourselves to download Python, but not yet...
     - name: Set up NuGet
-      uses: nuget/setup-nuget@v2.0.1
+      uses: nuget/setup-nuget@323ab0502cd38fdc493335025a96c8fdb0edc71f # v2.0.1
 
     - name: Set up Python 3.14.3
       run: |
@@ -74,7 +77,7 @@ jobs:
           --cov-report xml
 
     - name: 'Upload coverage'
-      uses: codecov/codecov-action@v5
+      uses: codecov/codecov-action@75cd11691c0faa626561e295848008c8a7dddffe # v5.5.4
       with:
         token: ${{ secrets.CODECOV_ORG_TOKEN }}