add group header, moderation menu, and pins strip

docs/nip29-migration-plan.md

@@ -278,7 +278,7 @@ result, and create a group on a relay that accepts `9007`.
 Read-mostly group management, the surfaces the sidebar gave up in Phase 2 plus the two writes
 that need Phase 0.
 
-- **Group details** — a dialog or sheet opened from the panel toolbar: name, picture, banner,
+- **Group details** — a dialog opened from the panel's header row: name, picture, banner,
   about, flags (`private`, `restricted`, `hidden`, `closed`, `livekit`, `parent`, `children`),
   admins with their role labels (`Group::admins().entries()`), the roles the relay advertises
   (`Group::roles()`), members when the relay publishes `39002` (`Group::members()`), and pins
@@ -287,11 +287,11 @@ that need Phase 0.
   `admins()`) → `group.delete_event(id, cx)`; Phase 0 makes the row disappear.
 - **Pin / unpin** — the same menu: `group.update_pins(pins, cx)` with the current list plus or
   minus `Pin::Event(id)`; show `Group::pins()` as a strip above the list.
-- **Leave** — toolbar `Leave…` opens a confirmation naming the group (`Leave "Pizza Lovers"?`);
+- **Leave** — header `Leave…` opens a confirmation naming the group (`Leave "Pizza Lovers"?`);
   on confirm `registry.leave(&key, cx)` and the panel closes (dispatch `ClosePanel`, as the
   screening dialog does).
 - **Fork / migration banner** — when `group.elsewhere()` is `Some(moved)`, a banner:
-  `This group may have moved to {relay}.` with a `Open` button calling
+  `This group may have moved to {relay}.` with a `Join` button calling
   `registry.join_key(moved, None, cx)`. Never auto-join: the NIP asks the client to offer.
 
 Validation: same commands; manually delete a message, pin and unpin, leave and re-join.
@@ -371,3 +371,8 @@ this repo; `coop_web` check is the proxy.
 - `Join` never happens implicitly — not from `10009` alone, and not from `elsewhere()`.
 - The old crates are deleted only at the end, so any phase can be stopped and the app still
   runs.
+- The dock renders no per-panel toolbar — `Panel::toolbar_buttons` is defined but never called —
+  so the group's `Details` and `Leave` actions live in a header row inside the panel.
+- The fork banner's button joins the target group rather than opening it: the panel holds no
+  dock handle and the plan's call is `join_key` alone; the joined group then appears in the
+  sidebar.