docs: rebuild README as project showcase

[Ev3rGan]

Summary

• replace the process-heavy root README with a Chinese-first project showcase and an aligned English entry
• present the value proposition, capabilities, quickstart, architecture, validation evidence, and project scope with a restrained visual hierarchy
• move detailed operational guidance into a documentation index plus DeepSeek, deterministic demo, architecture, and SWE-bench guides

Validation

• python -m ruff check .
• python -m ruff format --check .
• python -m mypy under an isolated Python 3.11 environment
• python -m pytest (364 passed, 2 skipped)
• python -m build
• deterministic success and failure demo matrix
• local-link, external-link, Mermaid parity, and whitespace checks