ci: fetch LFS in clippy and heal stale pointers in test (#109)

Self-hosted jobs share one working tree. Without lfs, actions/checkout
sets GIT_LFS_SKIP_SMUDGE=1, so an LFS file that clippy checks out first
lands as a pointer and later checkouts never rewrite it. That is why the
monad fixture from 0182f4d fails on dev-server-2 with
`Error("expected value", line: 1, column: 1)`.

`lfs: true` on clippy stops new pointers; `git lfs checkout` in test
replaces the ones already on disk from the fetched object cache.

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

Author: define-null

.github/workflows/tests.yaml

@@ -34,6 +34,11 @@ jobs:
     if: github.event_name == 'push' || !github.event.pull_request.draft
     steps:
       - uses: actions/checkout@v4
+        with:
+          # Self-hosted jobs share one working tree. Without lfs, checkout writes new LFS files
+          # as pointers and later checkouts never rewrite them, so `test` read pointers and the
+          # query fixtures failed. Objects are cached under .git/lfs, so this is cheap.
+          lfs: true
       - uses: dsherret/rust-toolchain-file@v1
       - uses: Swatinem/rust-cache@v2
         with:
@@ -66,6 +71,10 @@ jobs:
       - uses: actions/checkout@v4
         with:
           lfs: true
+      # `git lfs fetch` above only fills the object cache. Pointers that an earlier checkout
+      # without lfs left in the shared working tree are never rewritten by git, so replace
+      # them from the cache here.
+      - run: git lfs checkout
       - uses: dsherret/rust-toolchain-file@v1
       - uses: Swatinem/rust-cache@v2
         with: