Include plugin id in plugin MCP tool metadata

[mzeng-openai]

Adding the id of the plugin that contains the MCP (if any) so we can apply filters at plugin level.

Summary

• carry the plugin owner into MCP runtime provenance
• attach plugin_id to outbound plugin-backed MCP tool-call _meta
• avoid misattributing user-configured MCP servers that shadow plugin server names

Testing

• just fmt
• just fix -p codex-mcp
• just fix -p codex-core
• cargo test -p codex-mcp
• cargo test -p codex-core plugin_mcp_tool_call_request_meta_includes_plugin_id
• cargo test -p codex-core to_mcp_config_omits_plugin_id_when_user_server_shadows_plugin_mcp
• cargo test -p codex-core rebuild_preserving_session_layers_refreshes_plugin_derived_mcp_config
• git diff --check

Notes

• Attempted cargo test -p codex-core; it aborted in agent::control::tests::resume_agent_from_rollout_skips_descendants_when_parent_resume_fails with a stack overflow before the full suite completed.