fix: the chat tab no longer scrolls, and a group is listed or invite-only

**The chat tab was 8px too tall, at every window size.** The panel is sized from
JS to `viewport - top - 16`, which puts its bottom 16px above the fold — but it
sits inside `.main`, which adds 24px of padding below it. Eight pixels of
document past the window, whatever the window. Measured at 700, 900 and 1200:
`scrollHeight` 708, 908, 1208.

This is the second one of these — the sign-in card was `.page-center` and
`.layout` each reserving `100vh - 52px` — so it is now measured in the suite
rather than reasoned about. `tests/harness/scroll_probe.py` renders the real
markup against the real stylesheet and **runs the real `fit()` lifted out of
`app.js`**: a copy of the formula in a test would go on passing after the
original changed, which is exactly the bug being guarded.

The fix does not encode 24 anywhere. The first pass runs as before, then the
leftover is measured and taken off, so anything added below the panel later is
absorbed the same way. Now `scrollHeight == innerHeight` at all three heights,
nothing below the fold, and the panel still fills the room it has — that last
one has its own test, because shrinking the chat to 240px would satisfy every
other assertion here and be useless.

The Settings tab was measured too and is **not** a bug: it fits at 1200px and
overflows only when its content is genuinely taller than the window.

**Group creation asked one question twice.** Visibility and admission were
separate selectors that could only ever be set together — picking Public reached
over and set the policy — and two of the four combinations are meaningless. The
API already refused public+invite with a 422, so the form could build a request
that could not succeed. Private+open was accepted and should not have been: a
group anyone may join that nobody can find is a listing with the listing
removed, since joining goes through the node and there is no link to pass
around.

So: one selector, "who can join", and the request derives the rest. The API now
refuses the other impossible pair as well, with a message that says which way to
resolve it. Six locale strings the visibility box owned are deleted rather than
left unread in ten files, and the two surviving descriptions now say what each
choice means for who can *find* the group — with the word "public" gone from the
page, nothing else would have said it, and someone would publish a group without
meaning to.

865 tests pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 2 insertions, 8 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
index 4e0a332..89927bb 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
@@ -303,16 +303,11 @@ export default {
   'create_group.title': '创建群组',
   'create_group.name': '群组名称',
   'create_group.name_placeholder': '例如：家庭照片、项目文件…',
-  'create_group.visibility': '可见性',
-  'create_group.private': '私密',
-  'create_group.private_desc': '只有受邀成员才能看到并访问文件',
-  'create_group.public': '公开',
-  'create_group.public_desc': '任何人都可以发现并浏览此群组',
   'create_group.join_policy': '加入方式',
   'create_group.invite': '仅限邀请',
-  'create_group.invite_desc': '成员必须由管理员邀请',
+  'create_group.invite_desc': "成员须由管理员邀请，群组不会公开列出。",
   'create_group.open': '开放（任何人都可加入）',
-  'create_group.open_desc': '任何人都可以加入，无需批准',
+  'create_group.open_desc': "列入公开群组，任何人都能找到并无需批准即可加入。",
   'create_group.description': '简介',
   'create_group.description_hint': '这个群组是做什么的？（可选）',
   'create_group.submit': '创建',
@@ -422,5 +417,4 @@ export default {
   'group.leave_confirm': '退出“{name}”？您将失去其文件和聊天的访问权。您上传的文件仍留在 node 上，node 也会保留它为您固定的身份，直到其运营者将其移除。',
   'profile.title': '个人资料',
   'usermenu.profile': '个人资料',
-  'create_group.public_is_open': '任何人都可以找到并加入公开群组。若要挑选谁能进来，请创建为私密群组。',
 };