* feat(mac): swap dashboard titlebar buttons with sidebar state
The Control UI reports sidebar collapsed/width over a new openclawNav
WKScriptMessage; the titlebar accessory shows toggle+back/forward
right-aligned to the sidebar edge while expanded, and
toggle+search+new-session while collapsed. Search opens the command
palette and + opens the new-session surface via openclaw:native-*
events. Older gateway bundles that never report keep the shipped
toggle/back/forward layout.
Refs #105129
* docs: describe state-dependent mac titlebar buttons