Summary

• Add a built-in tool result compaction plugin for shrinking large tool outputs before they enter context.
• Wire plugin discovery/configuration and CLI plugin visibility.
• Document the plugin in the built-in plugins docs.

Test Plan

• pytest tests/test_tool_result_compaction_plugin.py tests/test_transform_tool_result_hook.py tests/hermes_cli/test_plugins.py tests/hermes_cli/test_plugins_cmd.py

Result: 152 passed