feat: AI commit messages, change tree, router behavesAs, sidebar times (v2.2.0)

- Changes panel: Files and Changes merged into one panel; the overview's
  groups drawn as a folder tree (compacted chains, file counts, fold,
  stage/unstage a whole folder)
- AI-suggested commit message for what is staged
  (POST /api/lanes/:id/git/commit-message, claude -p --safe-mode, haiku)
- AI Router: optional "Behaves as" Claude model id, written as
  modelPicker options into the router's --settings file (issue #56)
- Sidebar: session rows show last activity, live rows their start time;
  a closed Terminal row can be removed (DELETE /api/run/history/:id)
- Every pane's CLI starts only once a client is attached; claude panes
  no longer forced inline; tmux scrollbar one column wide
- Update notifier: "Check for updates" reopens a closed notice

client/src/pages/Workspace.tsx

@@ -61,8 +61,6 @@ import {
   PanelLeftClose,
   PanelRightClose,
   Maximize2,
-  FolderTree,
-  GitCompare,
   ChartColumn,
 } from "lucide-react";
 import { api } from "../lib/api";
@@ -120,17 +118,9 @@ import { DestructiveLaneModal } from "../components/lanes/DestructiveLaneModal";
 const CHANGES_OPEN_KEY = "agenthub.workspace.changesOpen";
 /** localStorage key for how wide the Changes panel is. */
 const CHANGES_SIZE_KEY = "agenthub.workspace.changesSize";
-/** localStorage key for the right panel's activity-bar tab. */
-const PANEL_TAB_KEY = "agenthub.workspace.panelTab";
 /** localStorage key for the last workspace shown, restored on a bare /workspace. */
 const SELECTED_KEY = "agenthub.workspace.selected";
 
-const PANEL_TABS = [
-  { id: "files", Icon: FolderTree },
-  { id: "changes", Icon: GitCompare },
-] as const;
-type PanelTab = (typeof PANEL_TABS)[number]["id"];
-
 /** The three widths the Changes panel cycles through, then closed. Reading a
  *  diff and watching a console want opposite amounts of room, and which one is
  *  "work" changes several times an hour — hence ONE control that steps
@@ -600,21 +590,6 @@ export function Workspace() {
   const [cwdSuggestions, setCwdSuggestions] = useState<CwdSuggestion[]>([]);
   const [paneHasActiveRun, setPaneHasActiveRun] = useState(false);
 
-  const [panelTab, setPanelTab] = useState<PanelTab>(() => {
-    try {
-      const saved = window.localStorage.getItem(PANEL_TAB_KEY) as PanelTab | null;
-      return saved && PANEL_TABS.some((x) => x.id === saved) ? saved : "changes";
-    } catch {
-      return "changes";
-    }
-  });
-  useEffect(() => {
-    try {
-      window.localStorage.setItem(PANEL_TAB_KEY, panelTab);
-    } catch {
-      /* the panel just forgets its tab between visits */
-    }
-  }, [panelTab]);
   // Whether the Changes panel is open. A viewer preference, so it lives in
   // localStorage and never reaches the server — same rule as the lane strip's
   // order (client/src/lib/laneOrderStorage.ts).
@@ -1231,36 +1206,17 @@ export function Workspace() {
                   typeof changesSize === "number" ? "" : CHANGES_WIDTH[changesSize]
                 }${changesFull ? "" : " min-w-[18rem] border-l border-border"}`}
               >
-                {/* Activity bar: Files · Changes · Sessions, then the resize
-                    control — the same height as the console's tab bar, so the
-                    two read as one header strip. */}
+                {/* Header: the title, Analyst, then the resize control — the
+                    same height as the console's tab bar, so the two read as
+                    one header strip. Files and Changes are ONE panel now; its
+                    own mode switcher moves between them. */}
                 <div
                   className="flex h-10 shrink-0 items-center gap-1 border-b border-border px-2"
                   role="toolbar"
                 >
-                  {PANEL_TABS.map(({ id, Icon }) => (
-                    <button
-                      key={id}
-                      type="button"
-                      data-testid={`panel-tab-${id}`}
-                      aria-pressed={panelTab === id}
-                      // Narrow, a tab switch leaves the open file (and its
-                      // edit); at full width the editor stays put.
-                      onClick={() =>
-                        panelTab !== id &&
-                        (changesFull ? setPanelTab(id) : afterDrop(() => setPanelTab(id)))
-                      }
-                      title={tLanes(`panel.${id}`)}
-                      aria-label={tLanes(`panel.${id}`)}
-                      className={`flex h-7 w-7 items-center justify-center rounded-md transition-colors ${
-                        panelTab === id
-                          ? "bg-accent/15 text-accent"
-                          : "text-fg-muted hover:bg-surface-4 hover:text-fg-primary"
-                      }`}
-                    >
-                      <Icon className="h-4 w-4" />
-                    </button>
-                  ))}
+                  <span className="px-1 text-xs font-medium text-fg-secondary">
+                    {tLanes("panel.changes")}
+                  </span>
                   {/* The opened session's analysis page — a page of its own. */}
                   <button
                     type="button"
@@ -1318,7 +1274,6 @@ export function Workspace() {
                       key={panelKey}
                       laneId={panelAt.laneId}
                       session={panelAt.session}
-                      tab={panelTab}
                       full={changesFull}
                       onDirtyChange={setChangesDirty}
                       // A sibling worktree forks from the lane's SOURCE repo when