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/index.js

@@ -88,6 +88,7 @@ const webhooksRouter = require("./routes/webhooks");
 const remoteSourcesRouter = require("./routes/remote-sources");
 const metricsRouter = require("./routes/metrics");
 const lanesRouter = require("./routes/lanes");
+const projectsRouter = require("./routes/projects");
 const locksRouter = require("./routes/locks");
 
 const APP_VERSION = (() => {
@@ -128,6 +129,7 @@ function createApp() {
   app.use("/api/ai-tools", aiToolsRouter);
   app.use("/api/run", runRouter);
   app.use("/api/lanes", lanesRouter);
+  app.use("/api/projects", projectsRouter);
   app.use("/api/locks", locksRouter);
   app.use("/api/alerts", alertsRouter);
   app.use("/api/webhooks", webhooksRouter);