feat(hub): group names unique per owner, shown as name@owner

A group's identity stays its UUID. What changes is that "the name is
unique" — until now an unenforced expectation — becomes real, scoped to the
owner account, and the owner's username is surfaced so two groups called
"photos" on different nodes can be told apart.

Hub:
- `groups` gains a functional unique index `uq_groups_owner_name` on
  `(admin_id, lower(name))` (model + migration c3d4e5f6a7b8). The migration
  pre-flights: if the data already clashes it aborts and lists the
  offending (admin_id, name) pairs rather than renaming anyone's group.
  meshbay.org checked clean.
- `create_group` trims the name, rejects blank (422) and an owner-scoped
  case-insensitive clash (409), with an IntegrityError backstop for the
  race, and returns `owner_username`.
- `owner_username` added to `/v1/groups/mine`, `GET /v1/groups` (local
  rows), `POST /v1/groups/{id}/join`, `GET /v1/admin/groups`.

SPA:
- new `static/group-name.js` — `<GroupName name owner [inline]>` renders the
  name with the `@owner` handle on a smaller grey line under it.
- used in the sidebar, the group-page header, Explore cards, the Admin
  groups table, and cross-group Search (via a widened `cacheGroupIndex`
  carrying the owner). Delete/leave confirmations show `name@owner` inline.
- federated Explore rows show `@<source_hub>` instead of an account.

Design record and the locked decisions: ~/next/groupnames.md (out of repo).
MNP unchanged. Tests: test_group_name_unique.py, test_group_name_migration.py.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018gKJ85aZyvEwarXMFzFEwi

1 files changed, 6 insertions, 2 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/group-settings.js b/packages/meshbay-hub/src/meshbay_hub/static/group-settings.js
index 60b0184..59d1456 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/group-settings.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/group-settings.js
@@ -1244,7 +1244,9 @@ function GroupSettingsPanel({ groupId, group, token, transportRef, gekRef,
             ${isOwner
               ? html`
                 <button class="admin-btn danger" onClick=${async () => {
-                  if (!confirm(t('group.delete_group_confirm', { name: group.name }))) return;
+                  if (!confirm(t('group.delete_group_confirm', {
+                    name: group.owner_username ? `${group.name}@${group.owner_username}` : group.name,
+                  }))) return;
                   try {
                     // Node detach first (reversible), then hub delete (irreversible)
                     if (nodeDetected && nodeGroupName) {
@@ -1263,7 +1265,9 @@ function GroupSettingsPanel({ groupId, group, token, transportRef, gekRef,
               `
               : html`
                 <button class="admin-btn danger" onClick=${async () => {
-                  if (!confirm(t('group.leave_confirm', { name: group.name }))) return;
+                  if (!confirm(t('group.leave_confirm', {
+                    name: group.owner_username ? `${group.name}@${group.owner_username}` : group.name,
+                  }))) return;
                   try {
                     await hubFetch('/v1/groups/' + groupId + '/leave',
                                    { method: 'POST', token });