feat(spaceshd): pinned workspace field

Add a `pinned` bool to the workspace model, threaded through proto
(Workspace + WorkspaceView + SetWorkspaceMeta), the registry, the
set_workspace_meta handler, persistence, the CLI mapping, and the Tauri
bridge. serde(default) keeps existing state.json compatible (pinned=false).
Backs the sidebar Favorites section.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/spaceshd/src/registry.rs

@@ -51,7 +51,7 @@ impl Registry {
         let order = self.workspaces.len() as u32;
         self.workspaces.insert(id.clone(), Workspace {
             id: id.clone(), path: key.clone(), name, group_id: None, order,
-            unread: false, layout: None, zoomed: None, surfaces: HashMap::new(),
+            unread: false, pinned: false, layout: None, zoomed: None, surfaces: HashMap::new(),
         });
         self.by_path.insert(key, id.clone());
         (id, true)
@@ -168,7 +168,7 @@ impl Registry {
         }).collect();
         WorkspaceView {
             id: w.id.clone(), path: w.path.clone(), name: w.name.clone(),
-            group_id: w.group_id.clone(), order: w.order, unread: w.unread,
+            group_id: w.group_id.clone(), order: w.order, unread: w.unread, pinned: w.pinned,
             layout: w.layout.clone(), zoomed: w.zoomed.clone(), surfaces,
         }
     }

crates/spaceshd/src/server.rs

@@ -461,12 +461,13 @@ async fn handle_request(
             let _ = out.send(ok(id, serde_json::Value::Null)).await;
         }
 
-        Cmd::SetWorkspaceMeta { workspace_id, name, group_id, unread, order } => {
+        Cmd::SetWorkspaceMeta { workspace_id, name, group_id, unread, order, pinned } => {
             let found = reg.workspace_mut(&workspace_id).map(|w| {
                 if let Some(n) = name { w.name = n; }
                 if let Some(g) = group_id { w.group_id = g; }
                 if let Some(u) = unread { w.unread = u; }
                 if let Some(o) = order { w.order = o; }
+                if let Some(p) = pinned { w.pinned = p; }
             }).is_some();
             if found {
                 if let Some(view) = reg.workspace_view(&workspace_id) {

crates/spaceshd/src/state_store.rs

@@ -92,6 +92,7 @@ mod tests {
                 group_id: None,
                 order: 0,
                 unread: false,
+                pinned: false,
                 layout: None,
                 zoomed: None,
                 surfaces: std::collections::HashMap::new(),