refactor: add Justfile; fix some clippy lints

Justfile

@@ -0,0 +1,35 @@
+[group('build')]
+build pkg:
+    cargo build --package {{ pkg }}
+alias b := build
+
+[group('build')]
+build-all:
+    cargo build --workspace
+alias ba := build-all
+
+[group('test')]
+test pkg:
+    cargo test --package {{ pkg }}
+alias t := test
+
+[group('test')]
+test-all:
+    cargo test --workspace
+alias ta := test-all
+
+[group('check')]
+check pkg:
+    cargo fmt --check --package {{ pkg }}
+    cargo clippy --package {{ pkg }} -- \
+        --no-deps \
+        --deny 'clippy::all'
+alias c := check
+
+[group('check')]
+check-all:
+    cargo fmt --check --all
+    cargo clippy --all -- \
+        --no-deps \
+        --deny 'clippy::all'
+alias ca := check-all