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.

server/__tests__/pty-attach.test.js

@@ -56,7 +56,9 @@ describe("pty-attach", () => {
   it("accepts a well-formed runId", () => {
     assert.doesNotThrow(() => ptyAttach.validateRunId("agenthub-lane-42"));
     assert.doesNotThrow(() => ptyAttach.validateRunId("agenthub-lane-42-3"));
-    assert.throws(() => ptyAttach.validateRunId("agenthub-lane-42-4"), /EBADRUNID/);
+    assert.doesNotThrow(() => ptyAttach.validateRunId("agenthub-lane-42-9"));
+    assert.throws(() => ptyAttach.validateRunId("agenthub-lane-42-10"), /EBADRUNID/);
+    assert.throws(() => ptyAttach.validateRunId("agenthub-lane-42-0"), /EBADRUNID/);
   });
 
   it("turns tmux mouse mode on for the session it attaches to", () => {