docs(contributing): Project Structure omits major packages (mcp, scan, delegate, llmloop, pathutil, …)

Summary

CONTRIBUTING.md "Project Structure" is stale compared to the current internal/ layout on main. New contributors get an incomplete mental model of entrypoints and package ownership.

What CONTRIBUTING currently lists under internal/

agent, config, diff, llm, model, session, tool, telemetry, viewer

Source: https://github.com/alibaba/open-code-review/blob/main/CONTRIBUTING.md

Packages present on main but missing from that tree

delegate, gitcmd, llmloop, mcp, pathutil, release, scan, stdout, suggestdiff

(Verified via public internal/ directory listing on main.)

Proposed fix

1. Refresh the Project Structure tree in CONTRIBUTING.md to match main
2. Keep short one-line purpose comments for each package
3. Sync i18n CONTRIBUTING copies if maintainers want parity (docs/i18n/CONTRIBUTING.*.md)

AI disclosure

Assisted by passive static analysis tooling; structure checked against public source. I reviewed the evidence myself.

Request

Please assign this issue to me (@Erebuzzz) before I implement so we avoid duplicate work. Happy to open a focused docs/ PR after assignment.