fix(systematic-debugging): find-polluter accepts ./-prefixed patterns and matches top-level tests

Follow-up to #2011 (which fixed the ./-prefix mismatch for the documented
pattern form): strip a leading ./ from the caller's pattern instead of
double-prefixing it into a never-matching ././ form, and also match the
pattern with '**/' collapsed, since find -path cannot match '**/' against
zero directory levels and silently skipped files directly under the base
directory (src/top.test.ts vs src/**/*.test.ts).

Adds a deterministic test suite for the script with a stubbed npm.

skills/systematic-debugging/find-polluter.sh

@@ -18,8 +18,13 @@ echo "🔍 Searching for test that creates: $POLLUTION_CHECK"
 echo "Test pattern: $TEST_PATTERN"
 echo ""
 
-# Get list of test files (find . emits ./-prefixed paths)
-TEST_FILES=$(find . -path "./$TEST_PATTERN" | sort)
+# Get list of test files (find . emits ./-prefixed paths, so accept the
+# pattern written with or without a leading ./)
+TEST_PATTERN="${TEST_PATTERN#./}"
+# find -path can't match '**/' against zero directory levels, so a pattern
+# like src/**/*.test.ts would skip src/top.test.ts; also try the pattern
+# with '**/' collapsed to cover files directly under the base directory.
+TEST_FILES=$(find . \( -path "./$TEST_PATTERN" -o -path "./${TEST_PATTERN//\*\*\//}" \) | sort -u)
 if [ -z "$TEST_FILES" ]; then
   TOTAL=0
 else

tests/systematic-debugging/test-find-polluter.sh

@@ -0,0 +1,90 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
+SCRIPT_UNDER_TEST="$REPO_ROOT/skills/systematic-debugging/find-polluter.sh"
+
+FAILURES=0
+TEST_ROOT="$(mktemp -d)"
+
+cleanup() {
+  rm -rf "$TEST_ROOT"
+}
+trap cleanup EXIT
+
+pass() {
+  echo "  [PASS] $1"
+}
+
+fail() {
+  echo "  [FAIL] $1"
+  FAILURES=$((FAILURES + 1))
+}
+
+assert_contains() {
+  local haystack="$1"
+  local needle="$2"
+  local description="$3"
+
+  if printf '%s' "$haystack" | grep -Fq -- "$needle"; then
+    pass "$description"
+  else
+    fail "$description (expected output to contain: $needle)"
+  fi
+}
+
+# Toy project: one top-level test, one nested test. A stubbed `npm` on PATH
+# creates the pollution marker whenever any test runs, so the first test file
+# executed is always identified as the polluter.
+setup_project() {
+  PROJECT="$TEST_ROOT/project"
+  rm -rf "$PROJECT"
+  mkdir -p "$PROJECT/src/feature" "$PROJECT/bin"
+  echo "test('top')" > "$PROJECT/src/top.test.ts"
+  echo "test('nested')" > "$PROJECT/src/feature/nested.test.ts"
+  cat > "$PROJECT/bin/npm" <<'EOF'
+#!/usr/bin/env bash
+touch pollution.marker
+EOF
+  chmod +x "$PROJECT/bin/npm"
+}
+
+# run_polluter <pattern> — runs the script in the toy project with the stub
+# npm first on PATH; captures combined output, never aborts on exit code.
+run_polluter() {
+  local pattern="$1"
+  rm -f "$PROJECT/pollution.marker"
+  (
+    cd "$PROJECT"
+    PATH="$PROJECT/bin:$PATH" "$SCRIPT_UNDER_TEST" 'pollution.marker' "$pattern" 2>&1
+  ) || true
+}
+
+echo "Test: documented pattern finds nested test files (issue #2008)"
+setup_project
+OUTPUT="$(run_polluter 'src/**/*.test.ts')"
+assert_contains "$OUTPUT" "FOUND POLLUTER" "documented pattern runs tests and detects pollution"
+
+echo "Test: documented pattern also finds top-level test files"
+setup_project
+OUTPUT="$(run_polluter 'src/**/*.test.ts')"
+assert_contains "$OUTPUT" "Found 2 test files" "src/**/*.test.ts matches src/top.test.ts and src/feature/nested.test.ts"
+
+echo "Test: ./-prefixed pattern matches the same files"
+setup_project
+OUTPUT="$(run_polluter './src/**/*.test.ts')"
+assert_contains "$OUTPUT" "Found 2 test files" "leading ./ on the pattern is accepted"
+
+echo "Test: non-matching pattern reports an honest zero"
+setup_project
+OUTPUT="$(run_polluter 'nomatch/**/*.test.ts')"
+assert_contains "$OUTPUT" "Found 0 test files" "empty result counts as 0, not 1"
+assert_contains "$OUTPUT" "No polluter found" "empty result exits via the clean path"
+
+echo ""
+if [ "$FAILURES" -gt 0 ]; then
+  echo "$FAILURES test(s) failed"
+  exit 1
+fi
+echo "All tests passed"