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.

client/src/i18n/locales/en/lanes.json

@@ -311,5 +311,32 @@
   "conflict.reset": "Cancel",
   "conflict.save": "Save and mark resolved",
   "changes.takeOursHint": "Keep your version of the whole file",
-  "changes.takeTheirsHint": "Take the incoming version of the whole file"
+  "changes.takeTheirsHint": "Take the incoming version of the whole file",
+  "projects.title": "Projects",
+  "projects.folders": "Folders",
+  "projects.newWorkspace": "New workspace in {{name}}",
+  "projects.refresh": "Refresh projects and worktrees",
+  "projects.hidden_one": "{{count}} hidden",
+  "projects.hidden_other": "{{count}} hidden",
+  "projects.pick": "Pick a workspace in the sidebar",
+  "row.primary": "primary",
+  "row.adopt": "Adopt",
+  "row.actions": "Workspace actions",
+  "row.hint": "Double-click to rename · drag or Alt+↑/↓ to reorder · right-click for actions",
+  "menu.start": "Start",
+  "menu.stop": "Stop",
+  "menu.rename": "Rename",
+  "menu.newHere": "New workspace here…",
+  "menu.copyPath": "Copy path",
+  "menu.reset": "Reset worktree…",
+  "menu.remove": "Delete workspace…",
+  "pane.slot": "slot {{n}}",
+  "pane.close": "Stop this pane's session",
+  "panel.files": "Files",
+  "panel.changes": "Changes",
+  "panel.sessions": "Sessions",
+  "sessions.empty": "No sessions in this workspace yet",
+  "sessions.resume": "Resume",
+  "sessions.open": "Open",
+  "sessions.search": "Filter sessions…"
 }