debrand: finish second-pass rename across website docs + evaluation harness

[kdairatchi]

Follow-up to PR #18, which intentionally scoped the first-pass debrand to SECURITY.md, two example READMEs/docstrings, and the sdk/js package description.

A grep for `AIO Sandbox` / `aio-sandbox` / `aio-deepagents` still returns matches in these user-facing locations that should be addressed in a second pass:

Website (user-facing, high-priority)

• `website/docs/{en,zh}/index.md`
• `website/docs/{en,zh}/404.md`
• `website/docs/{en,zh}/guide/start/{introduction,quick-start}.{md,mdx}`
• `website/docs/{en,zh}/guide/basic/{browser,code-server,file,mcp,proxy,shell}.{md,mdx}`
• `website/docs/{en,zh}/examples/{index,agent,browser,terminal}.md`
• `website/docs/{en,zh}/blog/{index,announcing-0}.mdx`
• `website/theme/components/HomeLayout.tsx`
• `website/rspress.config.ts`
• `website/i18n.json`
• `website/docs/README.md`

SDK / examples (medium)

• `sdk/python/setup.py` (long description)
• `examples/langgraph-deepagents-integration/{pyproject.toml,sandbox_backend.py,README.md}`
• `examples/langgraph-deepagents-integration/uv.lock` (regenerates; fine to leave)

Intentionally preserved

• `UPSTREAM_README.md` — this is the upstream README preserved verbatim; leave alone.
• `cybersandbox/SECURITY.md` line 21 — still references `agent-infra/sandbox` in the out-of-scope bullet on purpose (that's where upstream bugs should go).
• `evaluation/` — upstream eval harness, not a user-facing surface; rename only if we're maintaining it.

Rename rule

• Replace "AIO Sandbox" → "CyberSandbox" in user-facing prose.
• Replace image refs `ghcr.io/agent-infra/sandbox` → `ghcr.io/prowlrbot/cybersandbox` in docs only if the intent is to steer users toward our image.
• Keep upstream attribution banners ("forked from agent-infra/sandbox") — do not remove credit.
• Do NOT rename the npm package `@agent-infra/sandbox` (breaking change).
• Do NOT rename the Python package name or HTTP API paths.