fix: bd --no-db dep tree now shows complete tree (GH#836)

The memory storage GetDependencyTree was missing the root node at depth 0,
causing --no-db mode to only show dependencies without the root issue.

Fixed by:
- Adding root node at depth 0 before listing dependencies
- Setting ParentID on child nodes for proper tree rendering

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/storage/memory/tree_test.go

@@ -0,0 +1,66 @@
+package memory
+
+import (
+    "context"
+    "testing"
+
+    "github.com/steveyegge/beads/internal/types"
+)
+
+func TestGetDependencyTree_IncludesRoot(t *testing.T) {
+    m := New("")
+    
+    // Create parent and child issues
+    parent := &types.Issue{
+        ID:       "bd-7zka",
+        Title:    "Parent issue",
+        Status:   types.StatusOpen,
+        Priority: 3,
+    }
+    child := &types.Issue{
+        ID:       "bd-7zka.2",
+        Title:    "Child issue",
+        Status:   types.StatusOpen,
+        Priority: 3,
+        Dependencies: []*types.Dependency{
+            {IssueID: "bd-7zka.2", DependsOnID: "bd-7zka", Type: "blocks"},
+        },
+    }
+    
+    if err := m.LoadFromIssues([]*types.Issue{parent, child}); err != nil {
+        t.Fatalf("LoadFromIssues failed: %v", err)
+    }
+    
+    tree, err := m.GetDependencyTree(context.Background(), "bd-7zka.2", 50, false, false)
+    if err != nil {
+        t.Fatalf("GetDependencyTree failed: %v", err)
+    }
+    
+    // Should have 2 nodes: root at depth 0, dependency at depth 1
+    if len(tree) != 2 {
+        t.Errorf("Expected 2 nodes, got %d", len(tree))
+        for i, node := range tree {
+            t.Logf("  [%d] ID=%s, Depth=%d, ParentID=%s", i, node.ID, node.Depth, node.ParentID)
+        }
+        return
+    }
+    
+    // First node should be root at depth 0
+    if tree[0].ID != "bd-7zka.2" {
+        t.Errorf("Expected root ID 'bd-7zka.2', got '%s'", tree[0].ID)
+    }
+    if tree[0].Depth != 0 {
+        t.Errorf("Expected root depth 0, got %d", tree[0].Depth)
+    }
+    
+    // Second node should be dependency at depth 1
+    if tree[1].ID != "bd-7zka" {
+        t.Errorf("Expected dependency ID 'bd-7zka', got '%s'", tree[1].ID)
+    }
+    if tree[1].Depth != 1 {
+        t.Errorf("Expected dependency depth 1, got %d", tree[1].Depth)
+    }
+    if tree[1].ParentID != "bd-7zka.2" {
+        t.Errorf("Expected dependency ParentID 'bd-7zka.2', got '%s'", tree[1].ParentID)
+    }
+}