Help on every panel, task filter, unblock key, mouse zones, safe add-only rebuild

README.md

@@ -70,6 +70,11 @@ Choosing a task on the board and pressing Enter writes it into the project's
 
 - **`r`** — read the data again in this panel. Nothing closes, nothing moves, the
   layout is untouched. Use it when the numbers look stale.
+- **`B`** — on the Repair screen only: add whatever panes are missing without
+  closing any, so it is safe to press from inside a pane.
+- **`?`** — the keys for the panel you are in, as an overlay.
+- **`/`** — filter the task list by identifier, title or assignee name.
+- **`u`** — unblock a task whose blocker has finished but which still says blocked.
 - **`R`** — rebuild everything: `bin/board --replace` closes each pane the layout
   owns and builds all seven again, in order. It runs detached in its own session,
   because the panel you pressed it in is one of the panes being replaced; the