feat: workspace aliases, tab groups of split panes, native path picker (v2.1.0)

- /api/workspaces and `agenthub workspace(s)` / `--workspace` as aliases of
  /api/lanes and `agenthub lanes` / `--lane`; old names print one stderr note.
  REPL `help lanes|workspace|workspaces` resolves through the aliases.
- A workspace holds up to ten sessions (slots 0-9); every console tab is a
  group of 1-4 split panes (PaneGroups, agenthub.workspace.paneLayout);
  parseGroups keeps the stored active tab when an earlier one is dropped.
- Browse button beside path fields: POST /api/lanes/pick-path opens the OS
  picker on the server's desktop — loopback only and no forwarding header
  (EREMOTE), a display failure is ENODIALOG not a Cancel, the dialog is
  killed when the request closes, a folder field falls back to the in-app
  browser on any failure.
- Changes rail counts chip, image viewer (/git/raw), status bar session
  counts and per-day cost (`date=` on /api/pricing/cost).
- /agenthub-open and /agenthub-doctor run from the INSTALLED build
  (supersededBy), doctor offers fixes behind two confirmations; plugin-open
  treats a locked bootstrap as non-fatal.
- New-terminal shell waits for the first attach (issue #55).
- repo-onboarding / debug-live-issue skills removed.
- OpenAPI: pick-path, lane/date on /pricing/cost, tool on /run/history,
  /api/workspaces mount.

client/src/components/lanes/WorkspaceRow.tsx

@@ -6,8 +6,8 @@
  * session there) and `⋯` (the row menu, `WorkspaceRowMenu.tsx`, also on
  * right-click). Dragging it, or Alt+↑/↓, reorders the list — a viewer
  * preference kept in localStorage (`laneOrderStorage.ts`), never written to
- * the lane row. Only a workspace row's own drag (`LANE_DRAG_TYPE`) is taken —
- * a file, a tab or a text dragged over is not a reorder. F2 renames too; the
+ * the lane row. The row only STARTS a drag (`LANE_DRAG_TYPE`); the list
+ * (`WorkspaceTree.tsx`) takes the drop anywhere, gaps included. F2 renames too; the
  * dot's meaning is screen-reader text, and an idle dot is a ring.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
@@ -20,7 +20,7 @@ import { isSubmitEnter } from "../../lib/keys";
 
 /** What a workspace row's drag carries: its index in the list. */
 export const LANE_DRAG_TYPE = "application/x-agenthub-lane";
-const isLaneDrag = (e: { dataTransfer: DataTransfer | null }) =>
+export const isLaneDrag = (e: { dataTransfer: DataTransfer | null }) =>
   !!e.dataTransfer?.types?.includes(LANE_DRAG_TYPE);
 
 /** The row's dot: the lane's liveness, plus a running pulse and needs-you. */
@@ -78,7 +78,6 @@ export function WorkspaceRow({
 }) {
   const { t } = useTranslation("lanes");
   const [draft, setDraft] = useState("");
-  const [dropTarget, setDropTarget] = useState(false);
   const name = workspaceName(lane);
   const openMenu = (e: MouseEvent) => {
     e.preventDefault();
@@ -92,38 +91,20 @@ export function WorkspaceRow({
   return (
     <div
       data-testid={`workspace-row-${lane.id}`}
-      data-drop-target={dropTarget ? "true" : undefined}
+      data-lane-index={index}
       draggable={!renaming}
       onDragStart={(e) => {
         // Firefox starts no drag at all without a setData call.
         e.dataTransfer.setData(LANE_DRAG_TYPE, String(index));
         e.dataTransfer.effectAllowed = "move";
       }}
-      onDragOver={(e) => {
-        if (!isLaneDrag(e)) return;
-        e.preventDefault();
-        setDropTarget(true);
-      }}
-      onDragLeave={() => setDropTarget(false)}
-      onDragEnd={() => setDropTarget(false)}
-      onDrop={(e) => {
-        setDropTarget(false);
-        if (!isLaneDrag(e)) return;
-        e.preventDefault();
-        const raw = e.dataTransfer.getData(LANE_DRAG_TYPE);
-        // Number("") is 0: an empty payload must not move the first row.
-        const from = raw === "" ? NaN : Number(raw);
-        if (Number.isInteger(from)) onReorder(from, index);
-      }}
       onContextMenu={openMenu}
       className={`group flex items-center gap-1 rounded-md pl-1 pr-1 transition-colors ${
-        dropTarget
-          ? "bg-accent/20"
-          : selected
-            ? "bg-accent/10"
-            : lane.needs_action
-              ? "bg-status-warning/10 hover:bg-status-warning/20"
-              : "hover:bg-surface-3"
+        selected
+          ? "bg-accent/10"
+          : lane.needs_action
+            ? "bg-status-warning/10 hover:bg-status-warning/20"
+            : "hover:bg-surface-3"
       }`}
     >
       <button