tzif: support pathological transitions

.github/workflows/ci.yml

@@ -110,10 +110,14 @@ jobs:
       run: cargo build -p jiff-tzdb-platform --verbose
     - name: Build docs
       run: cargo doc --features serde --verbose
-    - name: Run library tests
-      run: cargo test --lib
-    - name: Run integration tests
-      run: cargo test --test integration
+    # We don't really care much about adding dev dependencies, and they can
+    # move quite a bit faster. So unfortunately don't run tests on MSRV. We
+    # could fix this by adding a `Carg.msrv.lock` or some such, but it doesn't
+    # seem worth it.
+    # - name: Run library tests
+      # run: cargo test --lib
+    # - name: Run integration tests
+      # run: cargo test --test integration
 
   # Generic testing for most cross targets. Some get special treatment in
   # other jobs.
@@ -231,7 +235,7 @@ jobs:
       # logs.
       TZ: America/New_York
     steps:
-    - uses: dtolnay/rust-toolchain@stable
+    - uses: dtolnay/rust-toolchain@1.81.0
     - uses: actions/checkout@v4
     - name: Install wasm-pack
       run: |