Summary

• add a long-term docs/sdlc-harness/ documentation tree for BitFun as an external-project SDLC Harness platform
• split the material into overview, design, implementation plan, external research, governance notes, architecture modules, and feature modules
• add concise root AGENTS.md and AGENTS-CN.md entries that direct future Harness-related changes to the design overview and module docs
• map the SDLC Harness logical layers back to the existing core decomposition and Agent Runtime Services development view
• refine Chinese wording across the docs and tracking issue to use clearer design-boundary, cost-control, and evidence-governance language
• omit the previous brief/simplified document from the maintained docs tree because the main design now serves as the overview entry

Related issue

• 规划 BitFun 可配置开发体验与工程治理能力建设 #1136

Validation

• professional wording scan over docs/sdlc-harness, AGENTS.md, AGENTS-CN.md, and issue 规划 BitFun 可配置开发体验与工程治理能力建设 #1136 returned no targeted colloquial risk terms
• stale-pattern scan over docs/sdlc-harness, AGENTS.md, and AGENTS-CN.md returned no unfinished markers or old brief references
• trailing-whitespace scan over docs/sdlc-harness, AGENTS.md, and AGENTS-CN.md returned no matches
• changed Markdown link target check returned ALL_CHANGED_MD_LINKS_EXIST
• git diff --check HEAD~1..HEAD