feat(ui): sidebar project tree, status bar and a tabbed workbench for workspaces

The Workspace page's lane strip moves into the sidebar as a project tree:
workspaces grouped by git repository (new GET /api/projects, cached in
memory, POST /api/projects/refresh), untracked worktrees with Adopt, inline
rename, drag/Alt+arrow ordering and a right-click row menu. The selected
workspace is the URL's ?lane=, one shared lane list feeds the tree, the new
bottom status bar and the page. The Changes panel gains an activity bar
(Files / Changes / Sessions, with resume), and split panes get a header.

server/routes/projects.js

@@ -0,0 +1,25 @@
+/**
+ * @file Express router for /api/projects: every lane grouped by the git repo
+ * it belongs to, with that repo's worktrees (see server/lib/projects.js). Read
+ * on demand by the sidebar's project tree, never polled; `POST /refresh` drops
+ * the cached roots and worktree lists first.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+const { Router } = require("express");
+const lanesLib = require("../lib/lanes");
+const { listProjects, clearProjectCaches } = require("../lib/projects");
+const { sameOriginGuard } = require("../lib/same-origin");
+
+const router = Router();
+
+router.get("/", async (_req, res) => {
+  res.json({ projects: await listProjects(lanesLib.listLanes()) });
+});
+
+router.post("/refresh", sameOriginGuard, async (_req, res) => {
+  clearProjectCaches();
+  res.json({ projects: await listProjects(lanesLib.listLanes()) });
+});
+
+module.exports = router;