docs: clarify current engineering scope and preserved evidence

[AlbertXXuu]

Problem and outcome

Current planning documents required outside-user recruitment and a weekly update quota, while two Studio descriptions called the implemented return-to-top wordmark non-interactive. The current plan now uses reproducible engineering milestones, preserves historical plans as references, and documents the actual wordmark behavior consistently in English and Chinese.

Scope

Twelve documentation files. Runtime code, report schemas, immutable evidence, published tags and dependencies are unchanged. External adoption remains an observed outcome; mock results remain separate from real-model capability.

Evidence

• python scripts/check_repository.py: passed, 196 text files / 297 Markdown links / 1056 JSON or JSONL documents.
• git diff --check, changed-document local-link audit and introduced-secret/path scan: passed.
• Reused unchanged stage-one validation: offline contributor smoke produced 3/3 records; frozen report verification matched 4 sources and 5 outputs; the existing accessible-home-control test passed.
• Full supported-runtime, wheel and Studio checks run in this PR's existing CI.

Compatibility and risk

Documentation only; no new API, model run or evidence claim. The wordmark description preserves URL/workspace state, top-position behavior and reduced-motion behavior already implemented.