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, 42 insertions, 16 deletions

diff --git a/packages/meshbay-hub/tests/test_transport_contracts.py b/packages/meshbay-hub/tests/test_transport_contracts.py
index 8d975d7..5da8104 100644
--- a/packages/meshbay-hub/tests/test_transport_contracts.py
+++ b/packages/meshbay-hub/tests/test_transport_contracts.py
@@ -129,6 +129,14 @@ def test_presence_has_three_states_and_a_label_for_each(app):
         "the dot needs a title and an aria-label, not just a colour")
 
 
+def _string(source: str, key: str) -> str:
+    """One locale entry's text, whether it is written on one line or spliced
+    across several with `+`."""
+    start = source.index(f"'{key}':") + len(f"'{key}':")
+    end = source.index("\n  '", start)
+    return source[start:end]
+
+
 def test_a_refusal_from_the_node_counts_as_present(app):
     """The node answering "no" proves it is up; only silence proves nothing."""
     assert "err.reason ? 'online' : 'offline'" in app
@@ -136,30 +144,48 @@ def test_a_refusal_from_the_node_counts_as_present(app):
 
 # ── The create-group form ─────────────────────────────────────────────────────
 
-def test_choosing_public_settles_the_admission_question(app):
-    """Public implies open, so the policy selector has nothing left to ask.
-
-    Enforced twice on purpose: the API refuses public+invite with a 422, and the
-    form never offers the combination. A form that can build a request the server
-    rejects is a form that produces an error message instead of a group.
+def test_the_form_asks_one_question_not_two(app):
     """
-    assert "setVisibility('public'); setJoinPolicy('open');" in app, (
-        "picking Public must settle the policy, not leave the previous one")
-    assert "setVisibility('private'); setJoinPolicy('invite');" in app, (
-        "going back to Private must not leave the group open by accident")
+    Visibility and admission were separate selectors that could only ever be set
+    together, and the form knew it — picking Public reached over and set the
+    policy. Two of the four combinations were impossible: the API refused
+    public+invite with a 422, and private+open is a directory listing nobody can
+    find, joining being through the node rather than a link.
 
+    So there is one selector. "Open" is what makes a group listed, and the
+    request derives the rest.
+    """
     form = app[app.index("function CreateGroupPage"):]
     form = form[:form.index("\n}\n")]
-    selector = form.index("t('create_group.join_policy')")
-    guard = form.rindex("visibility === 'public'", 0, selector)
-    assert guard != -1, "the policy selector must sit behind a visibility guard"
-    assert "create_group.public_is_open" in form[guard:selector], (
-        "a public group should say why there is nothing to choose")
+
+    assert "setVisibility(" not in form, "the visibility selector is back"
+    assert "t('create_group.join_policy')" in form
+    assert "joinPolicy === 'open' ? 'public' : 'private'" in form, (
+        "the request must derive visibility rather than leave it unset")
+
+
+def test_the_form_says_what_each_choice_means_for_finding_the_group(app):
+    """Dropping the visibility box removes the words "public" and "private"
+    from the page. If the descriptions do not say it, nothing does — and
+    somebody publishes a group without meaning to."""
+    en = (STATIC / "locales" / "en.js").read_text(encoding="utf-8")
+    invite = _string(en, "create_group.invite_desc")
+    open_ = _string(en, "create_group.open_desc")
+    assert "not listed" in invite.lower()
+    assert "listed" in open_.lower() and "anyone" in open_.lower()
+
+
+def test_the_strings_the_visibility_box_used_are_gone(app):
+    """A key nobody reads is a key that rots, and ten locales carry each one."""
+    for locale in (STATIC / "locales").glob("*.js"):
+        text = locale.read_text(encoding="utf-8")
+        for key in ("create_group.visibility", "create_group.private",
+                    "create_group.public_is_open", "create_group.public_desc"):
+            assert f"'{key}'" not in text, f"{locale.name} still carries {key}"
 
 
 def test_the_form_starts_on_a_combination_the_api_accepts(app):
     form = app[app.index("function CreateGroupPage"):]
-    assert "useState('private')" in form[:form.index("return html")]
     assert "useState('invite')" in form[:form.index("return html")]