fix(maestro): fold the sole root sidebar folder into its own children

~ never distinguishes anything from a sibling — nothing else sits
beside it — so it showed as its own header even when it immediately
branched into multiple real projects. Now it folds into each child
instead, at the top only; a real divergence further down still gets
its own header.

web/src/tree.test.ts

@@ -39,6 +39,16 @@ describe("buildTree", () => {
     expect(names(root)).toEqual(["~/git/naps62/maestro"]);
   });
 
+  it("folds the sole root folder into each of its own children when it branches", () => {
+    const root = buildTree(
+      [session("a", "/home/n/subvisual/bullish"), session("b", "/home/n/tea/maestro")],
+      "/home/n",
+      "",
+    ) as TreeFolder;
+
+    expect(names(root).sort()).toEqual(["~/subvisual/bullish", "~/tea/maestro"]);
+  });
+
   it("stops collapsing where a directory branches", () => {
     const root = buildTree(
       [session("a", "/home/n/git/one"), session("b", "/home/n/git/two")],

web/src/tree.ts

@@ -59,6 +59,15 @@ export function buildTree(sessions: Session[], home: string | undefined, filter:
     for (const c of n.children) if (c.kind === "folder") sortRec(c);
   };
   sortRec(root);
+  // The root's sole child (usually `~`) has no sibling to distinguish it
+  // from, so it folds into every one of its own children, not just a lone
+  // one — unlike the chain merge below, and only here at the very top.
+  if (root.children.length === 1 && root.children[0].kind === "folder") {
+    const only = root.children[0];
+    root.children = only.children.map((c) =>
+      c.kind === "folder" ? { ...c, name: `${only.name}/${c.name}` } : c,
+    );
+  }
   // Collapse linear directory chains so `~/git.naps.pt/naps62/maestro` reads as
   // one compact folder rather than four nested ones.
   root.children = root.children.map((c) => (c.kind === "folder" ? mergeLinear(c) : c));