Runs cargo-udeps on nightly weekly (Mondays at 9am UTC) and on-demand
via workflow_dispatch, keeping it out of the PR critical path so nightly
breakage doesn't block merges.

https://claude.ai/code/session_01RnYQHGtVmViNLvadCJNZ38

diff --git a/.github/workflows/udeps.yml b/.github/workflows/udeps.yml
new file mode 100644
index 0000000..6fbce7d
--- /dev/null
+++ b/.github/workflows/udeps.yml
@@ -0,0 +1,22 @@
+name: Udeps
+
+on:
+  schedule:
+    - cron: '0 9 * * 1' # Every Monday at 9am UTC
+  workflow_dispatch:
+
+permissions: {}
+
+jobs:
+  udeps:
+    name: Unused dependencies
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - run: rustup toolchain install nightly --no-self-update
+      - run: cargo install cargo-udeps --locked
+      - run: cargo +nightly udeps --workspace