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/routes/pricing.js

@@ -477,6 +477,12 @@ router.get("/cost", (req, res) => {
       .status(400)
       .json({ error: { code: "INVALID_INPUT", message: "lane must be a lane id" } });
   }
+  const date = req.query.date;
+  if (date !== undefined && !/^\d{4}-\d{2}-\d{2}$/.test(String(date))) {
+    return res
+      .status(400)
+      .json({ error: { code: "INVALID_INPUT", message: "date must be YYYY-MM-DD" } });
+  }
   const scope = sourceColumnClause(parseSources(req), "s.source");
   const params = [...scope.params];
   const where = scope.clause ? [scope.clause] : [];
@@ -489,7 +495,9 @@ router.get("/cost", (req, res) => {
   }
   const whereClause = where.length ? `WHERE ${where.join(" AND ")}` : "";
 
-  const dailyTokens = dailyTokenRows(tzModifier, whereClause, params);
+  let dailyTokens = dailyTokenRows(tzModifier, whereClause, params);
+  // `date=`: only that local day (the status bar's Today and its per-model list).
+  if (date !== undefined) dailyTokens = dailyTokens.filter((r) => r.date === date);
   const rules = stmts.listPricing.all();
   // Price the date-split rows so each day's usage bills at the rate effective on
   // that date (e.g. Sonnet 5's intro discount before 2026-08-31, standard after).