test(config-audit): add marketplace-small/medium/large scanner fixtures

plugins/config-audit/tests/fixtures/marketplace-large/.claude/shared-tests.md

@@ -0,0 +1,9 @@
+# Shared Test Patterns
+
+- One fixture per scenario under `tests/fixtures/{name}/`
+- `describe(...)` + `it(...)` from `node:test`
+- Co-locate tests with their implementation as `*.test.mjs`
+- Prefer table-driven tests for permutations
+- Reset module-level state in `beforeEach` to keep tests isolated
+- Use `execFile` for CLI subprocess tests
+- Avoid mocks for I/O at fixture boundaries — read real files instead