feat: add flake-checker workflow

Run flake health checks on PRs and pushes to master using
DeterminateSystems actions with FlakeHub caching.

Author: typedrat

.github/workflows/flake-checker.yml

@@ -0,0 +1,21 @@
+# This file is automatically generated from Nix configuration. Do not edit directly.
+
+jobs:
+  check:
+    permissions:
+      contents: read
+      id-token: write
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/determinate-nix-action@v3
+      - uses: DeterminateSystems/flakehub-cache-action@main
+      - uses: DeterminateSystems/flake-checker-action@main
+      - run: nix flake check
+name: Flake Checker
+"on":
+  pull_request: {}
+  push:
+    branches:
+      - master
+  workflow_dispatch: {}

dev/flake-module.nix

@@ -99,6 +99,45 @@
           };
         };
 
+        flake-checker = {
+          name = "Flake Checker";
+
+          on = {
+            pullRequest = {};
+            workflowDispatch = {};
+            push.branches = ["master"];
+          };
+
+          jobs = {
+            check = {
+              runsOn = "ubuntu-latest";
+
+              permissions = {
+                id-token = "write";
+                contents = "read";
+              };
+
+              steps = [
+                {
+                  uses = "actions/checkout@v4";
+                }
+                {
+                  uses = "DeterminateSystems/determinate-nix-action@v3";
+                }
+                {
+                  uses = "DeterminateSystems/flakehub-cache-action@main";
+                }
+                {
+                  uses = "DeterminateSystems/flake-checker-action@main";
+                }
+                {
+                  run = "nix flake check";
+                }
+              ];
+            };
+          };
+        };
+
         update-flake-lock = {
           name = "Update flake.lock";