Build on a named SDK, and keep the .NET 8 runtime for the net8.0 tests

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
         with:
           dotnet-version: |
             8.0.x
-            10.0.x
+          global-json-file: global.json
 
       # Named, so the failure can say what to do about it. NU1004 on a Dependabot branch means
       # the lock files were not regenerated, which is a chore rather than a defect -- and the
@@ -63,7 +63,7 @@ jobs:
         with:
           dotnet-version: |
             8.0.x
-            10.0.x
+          global-json-file: global.json
 
       - name: Restore
         run: dotnet restore --locked-mode

.github/workflows/publish.yml

@@ -57,7 +57,7 @@ jobs:
         with:
           dotnet-version: |
             8.0.x
-            10.0.x
+          global-json-file: global.json
 
       - name: Resolve version
         id: version

.github/workflows/refresh-lock-files.yml

@@ -51,7 +51,7 @@ jobs:
         with:
           dotnet-version: |
             8.0.x
-            10.0.x
+          global-json-file: global.json
 
       # --force-evaluate is the whole point: it re-resolves rather than asserting the lock is right.
       - run: dotnet restore --force-evaluate

global.json

@@ -0,0 +1,7 @@
+{
+  "sdk": {
+    "version": "10.0.303",
+    "rollForward": "latestPatch",
+    "allowPrerelease": false
+  }
+}