fix(test): parse BUILD_FLAGS and TEST_FLAGS (#371)

* refactor(test): replace eval with bash arrays in unit function

Use read -ra to parse BUILD_FLAGS and TEST_FLAGS into arrays, so empty
variables expand to zero arguments without needing eval. This avoids
potential issues with shell metacharacter expansion.

https://claude.ai/code/session_01L1fN5BiN9pbngSFbtEPRWL

* fix(test): handle empty arrays under nounset on older bash

Use ${arr[@]+"${arr[@]}"} pattern to safely expand potentially empty
arrays. Bash 3.2 (macOS default) treats empty array expansion as an
unbound variable error under set -o nounset.

https://claude.ai/code/session_01L1fN5BiN9pbngSFbtEPRWL

---------

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

Author: KSXGitHub

test.sh

@@ -54,10 +54,12 @@ run_if() (
 )
 
 unit() (
-  eval run_if "${LINT:-true}" cargo clippy "$@" -- -D warnings
-  eval run_if "${DOC:-false}" cargo doc "$@"
-  eval run_if "${BUILD:-true}" cargo build "${BUILD_FLAGS:-}" "$@"
-  eval run_if "${TEST:-true}" cargo test "${TEST_FLAGS:-}" "$@"
+  read -ra build_flags <<<"${BUILD_FLAGS:-}"
+  read -ra test_flags <<<"${TEST_FLAGS:-}"
+  run_if "${LINT:-true}" cargo clippy "$@" -- -D warnings
+  run_if "${DOC:-false}" cargo doc "$@"
+  run_if "${BUILD:-true}" cargo build ${build_flags[@]+"${build_flags[@]}"} "$@"
+  run_if "${TEST:-true}" cargo test ${test_flags[@]+"${test_flags[@]}"} "$@"
 )
 
 run_if "${FMT:-true}" cargo fmt -- --check