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__/daily-cost.test.js

@@ -139,6 +139,13 @@ describe("GET /api/pricing/cost daily split", () => {
       "2026-10-05": 3,
     });
     assert.equal(ict.body.total_cost, 7);
+
+    // `date=` prices that one local day, breakdown included.
+    const day = await call("GET", "/api/pricing/cost?tz_offset=-420&date=2026-10-03");
+    assert.equal(day.body.total_cost, 2);
+    assert.equal(day.body.breakdown.length, 1);
+    assert.equal(day.body.breakdown[0].input_tokens, 2 * M);
+    assert.equal((await call("GET", "/api/pricing/cost?date=10/03")).status, 400);
   });
 
   it("scales hours above the total down to it, so the days still add up", async () => {