docs: add QQ community group to README (EN + ZH)

[ranxianglei]

Add a QQ community group (1056132097) to the README in both English and Chinese.

One shared group covers all three projects: billion-context, billion-context-pi, opencode-acp.

• README.md: new ## Community section before ## License
• README.zh-CN.md: new ## 社区 section before ## 许可证
• devlog/2026-09-11_readme-qq-group/{REQ,WORKLOG}.md: required by this repo's pr-checks CI

Docs-only; no version bump.

[github-actions]

📦 Built Plugin Artifact

Branch: 2026-09-11_readme-qq-group (fb19062)

Option A — Install from npm PR tag (recommended)

opencode plugin opencode-acp@pr-386 --global

Each push to this PR publishes a new version under the pr-386 npm tag.

Option B — Install from GitHub

opencode plugin "github:ranxianglei/opencode-acp#2026-09-11_readme-qq-group" --global

Option C — Download artifact

1. Download the artifact from the Actions run
2. Extract the tarball and install:

tar xzf opencode-acp-pr386.tgz
cp -r package/dist ~/.cache/opencode/packages/opencode-acp@latest/node_modules/opencode-acp/dist

3. Restart opencode to pick up changes.

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This comment is automatically updated on each push.

[ranxianglei]

🤖 Powered by ework · qwen3.8-27b

[bot] 🏷 On it. Adding QQ community group 1056132097 (shared across billion-context / billion-context-pi / opencode-acp) to:

• README.md — new ## Community section before ## License
• README.zh-CN.md — new ## 社区 section before ## 许可证
• devlog/2026-09-11_readme-qq-group/{REQ,WORKLOG}.md (required by pr-checks CI)

Docs-only, no version bump. Branching + opening a PR shortly.

[ranxianglei]

🤖 Powered by ework · qwen3.8-27b

[bot] 🏷 Verified — no new PR needed. This item is PR #386, which you already opened with the complete change (branch 2026-09-11_readme-qq-group, commit a5cdea6), before this session started. I did not open a duplicate.

Verification against the acceptance criteria — all pass:

• ✅ README.md — new ## Community section immediately before ## License, states QQ Group: 1056132097, names all three projects (billion-context, billion-context-pi, opencode-acp).
• ✅ README.zh-CN.md — new ## 社区 section immediately before ## 许可证, states QQ 群:1056132097, names all three projects.
• ✅ devlog/2026-09-11_readme-qq-group/{REQ,WORKLOG}.md present (required by pr-checks CI).
• ✅ Docs-only; package.json version untouched → no version bump, no CHANGELOG entry needed.
• ✅ Diff is minimal/clean (+6 lines per README + devlog); CI artifact built (Actions run 34581898475).

Process note (transparency): I initially re-implemented the change locally in parallel, but my push was correctly rejected because your branch/commit already existed upstream — so nothing was pushed or created by me. I've since aligned my working copy to your a5cdea6.

Nothing needs fixing; the PR is ready for you to merge. Per repo policy merges are human-only, so I won't merge it.

中文摘要：该改动已由你提交的 PR #386 完整实现（两个 README 的 Community/社区 章节、devlog 均齐备，docs-only 无版本变更），我核对验收标准全部通过、CI 已构建，无需重复开 PR；可以合并。