lint: catch setup_suite PATH rewrites that hide Bats libexec

[junior-ricon]

Problem

BATS 1.13.0 can fail before running any tests when test/setup_suite.bash mutates PATH after Bats has started.

The common KKL pattern is:

setup_suite() {
  REPO_DIR="$(cd "$BATS_TEST_DIRNAME/.." && pwd)"
  export REPO_DIR
  eval "$(cd "$REPO_DIR" && mise env)"
}

mise env may rebuild PATH and drop Bats' libexec directory. Bats 1.13.0 then calls bats-exec-file by bare name from bats-exec-suite, producing:

bats-exec-suite: line 323: bats-exec-file: command not found
# bats warning: Executed 0 instead of expected N tests

This showed up in KnickKnackLabs/template after copying the skeleton into a workbench and running mise run test locally.

Related upstream fix: bats-core/bats-core#1209

Current local workaround

Preserve Bats' libexec path across mise env:

setup_suite() {
  REPO_DIR="$(cd "$BATS_TEST_DIRNAME/.." && pwd)"
  export REPO_DIR

  bats_libexec="${BATS_LIBEXEC:-}"
  eval "$(cd "$REPO_DIR" && mise env)"
  if [ -n "$bats_libexec" ]; then
    export PATH="$bats_libexec:$PATH"
  fi
}

This pattern already existed in KnickKnackLabs/emails; it was ported to KnickKnackLabs/template in 40be222.

Proposed lint

Add a codebase lint rule that flags test/setup_suite.bash files that:

1. call mise env or otherwise clearly evaluate tool-manager env that can rewrite PATH; and
2. do not preserve BATS_LIBEXEC across that call.

Possible rule name: bats-setup-suite-path or bats-libexec-preserved.

Suggested fixtures

Passing:

• setup suite with no mise env / no PATH rewrite;
• setup suite that saves ${BATS_LIBEXEC:-} before mise env and prepends it afterward;
• no test/setup_suite.bash.

Failing:

• current old template shape: eval "$(cd "$REPO_DIR" && mise env)" with no BATS_LIBEXEC preservation.

Notes

When upstream Bats releases the fix and KKL repos move past Bats 1.13.0, this rule may become less necessary. Until then, the lint would prevent template-seeded repos from inheriting a known local/macOS failure mode.