fix: Alpine x-for errors — tree init + unique keys + _loaded guard

- tree starts as [] (not undefined) so x-for doesn't crash
- :key uses node.db_id || 'item-'+idx for uniqueness
- _loaded guard prevents rendering before async init completes
- Empty state shows while loading, tree only renders after load()

app/templates/local_workspace.html

@@ -71,8 +71,8 @@
   </div>
 
   <!-- Recursive tree -->
-  <ul class="ws-tree" x-show="tree.length">
-    <template x-for="node in tree" :key="node.id">
+  <ul class="ws-tree" x-show="tree.length && _loaded">
+    <template x-for="(node, idx) in tree" :key="node.db_id || 'item-'+idx">
       <li>
         <div class="ws-tree-item"
              :data-id="node.db_id"
@@ -162,6 +162,7 @@ function wsPage() {
     createType: 'file', newName: '', parentFolder: null,
     renameTarget: null, deleteTarget: null,
     expandedFolders: {},
+    _loaded: false,
 
     async init() { await this.load(); },
 
@@ -170,7 +171,8 @@ function wsPage() {
         const r = await fetch('/api/local-workspace/tree');
         const data = await r.json();
         this.tree = this.flattenTree(data.tree || [], 0);
-      } catch(e) { console.error(e); }
+        this._loaded = true;
+      } catch(e) { console.error(e); this._loaded = true; }
     },
 
     flattenTree(nodes, depth) {