fix: P1 shell tooltip fixes + Today routing + workspaces API

Shell:
- WorkspaceHost: change tooltip from pluginId to human-readable title
- StatusBar: replace pluginId tooltips with label or id (3 occurrences)
- App: startup routing to Today view, sidebar Today nav item
- Sidebar: add Today button in Overview section
- TodaySurface: separate global vs workspace data (no fallthrough)

Plugin API:
- Add workspaces.list() method wrapping App.ListWorkspaces()
  (needed by browser-inbox workspace picker)

frontend/src/lib/shell/StatusBar.svelte

@@ -95,7 +95,7 @@
         class:status-bar-warning={item.handler}
         class="status-bar-item"
         data-status-item-id={item.id}
-        title={item.handler ? `${item.pluginId}: compact status only` : item.pluginId}
+        title={item.handler ? `${item.pluginId}: click for details` : (item.label || item.id)}
       >
         {#if item.handler}<Icon name="warning" size={11} class="status-warning-icon" />{/if}
         {item.label || item.id}
@@ -108,7 +108,7 @@
         class:status-bar-warning={item.handler}
         class="status-bar-item"
         data-status-item-id={item.id}
-        title={item.handler ? `${item.pluginId}: compact status only` : item.pluginId}
+        title={item.handler ? `${item.pluginId}: click for details` : (item.label || item.id)}
       >
         {#if item.handler}<Icon name="warning" size={11} class="status-warning-icon" />{/if}
         {item.label || item.id}
@@ -121,7 +121,7 @@
         class:status-bar-warning={item.handler}
         class="status-bar-item"
         data-status-item-id={item.id}
-        title={item.handler ? `${item.pluginId}: compact status only` : item.pluginId}
+        title={item.handler ? `${item.pluginId}: click for details` : (item.label || item.id)}
       >
         {#if item.handler}<Icon name="warning" size={11} class="status-warning-icon" />{/if}
         {item.label || item.id}