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/settings/HomeDirSetting.tsx

@@ -17,6 +17,7 @@ import { AlertTriangle, FolderOpen } from "lucide-react";
 import { confirmDialog } from "../../lib/confirm";
 import { isSubmitEnter } from "../../lib/keys";
 import { SettingsSection } from "./SettingsRow";
+import { PathPickButton } from "../PathPickButton";
 
 export interface HomeDirValue {
   value: string;
@@ -122,6 +123,13 @@ export function HomeDirSetting({
             className="input flex-1 font-mono"
             placeholder={placeholder}
           />
+          <PathPickButton
+            start={input}
+            onPick={(p) => {
+              setInput(p);
+              setError(null);
+            }}
+          />
           <button
             type="button"
             onClick={handleSave}