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/PageTabs.tsx

@@ -87,9 +87,9 @@ export function PageTabs({
             aria-controls={hasPanel && isActive ? panelId : undefined}
             tabIndex={isActive ? 0 : -1}
             onClick={() => onSelect(id)}
-            className={`inline-flex items-center gap-1.5 text-xs whitespace-nowrap px-3 py-1.5 rounded-lg border transition-colors flex-shrink-0 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-accent/60 ${
+            className={`inline-flex items-center gap-1.5 text-xs font-medium whitespace-nowrap px-3 py-1.5 rounded-lg border transition-colors flex-shrink-0 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-accent/60 ${
               isActive
-                ? "bg-accent/15 border-accent/30 text-accent font-semibold shadow-[inset_0_-2px_0_rgb(var(--accent))]"
+                ? "bg-accent/15 border-accent/30 text-accent shadow-[inset_0_-2px_0_rgb(var(--accent))]"
                 : "border-border text-fg-secondary hover:text-fg-primary hover:bg-surface-3"
             }`}
           >