docs: clarify Harness of Harnesses as next-version direction

[cyfyifanchen]

Summary

• Clarify that the current public Raven release is the runnable self-improving Agent Harness.
• Present The Harness of Harnesses as Raven's next-version direction and internal research prototype, not a capability of the current public release.
• Align the English and Chinese banner notes, section headings, future-tense descriptions, and benchmark labels around that release boundary.

Type

• Fix
• Feature
• Docs
• CI / tooling
• Refactor
• Other

Verification

• Relevant tests pass locally - not run because this is a docs-only change.
• Relevant lint / type checks pass locally - .venv/bin/pre-commit run --files README.md README.zh-CN.md passed.
• User-facing docs or screenshots are updated when needed
• UV_CACHE_DIR=/private/tmp/raven-uv-cache make check-large-files passed.
• git diff --check origin/main...HEAD passed.

Risk

• Security impact considered - no runtime code or dependencies changed.
• Backward compatibility considered - documentation only.
• Rollback path is clear for risky changes - revert the documentation commit.

Related Issues

N/A

[gloryfromca]

No blockers; this can merge as far as I am concerned.

I reviewed the complete github/main...HEAD diff. The English and Chinese READMEs consistently distinguish the runnable current public release from the next-version Harness of Harnesses direction, and both attribute the benchmark table to the internal research prototype. I found no concrete failure after checking the preceding positioning change and the surrounding README content.

Coverage: I checked AGENTS.md/CLAUDE.md and CONTEXT-MAP.md (the newly used positioning terms have no conflicting glossary entry), the full diff, bilingual parity, predecessor history, backward compatibility, and test integrity. There are no code callers or runtime behavior changes, and no tests were changed or weakened.

Verification: uv run --frozen --python 3.12 --extra dev pre-commit run --files README.md README.zh-CN.md, the underlying scripts/check_large_files.py github/main..HEAD check, git diff --check github/main...HEAD, and the merge-tree check against current GitHub main all passed. The make check-large-files wrapper itself could not run because make is unavailable in this environment; its exact Python check passed directly. GitHub's pre-commit, lint, repository-file, TUI, bridge, Windows upgrade, title, and commit-message checks were passing when reviewed; the full unit job was still pending. Full local runtime tests were not run because this is a documentation-only change.