docs: add benchmark-informed full codebase deep review report

Research-backed review against 6 top Python MCP server projects
and official MCP specification. 13 findings (2 critical, 6 warning,
5 info) — all fixed in preceding commit.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ayhammouda