refactor: dedupe the jscpd clones; drop the baseline loading gate

- Extract the shared New Session action into WorkspacesService.startSession
  (sidebar button and workspace browser both delegate; recent-Workspace
  targeting and the no-workspace clear live in one place).
- Fold the chip-insertion transaction shared by insert-ref and paste-upgrade
  into one InputMachine helper.
- Share the fixture's session-not-found guard across the sessionId-addressed
  catalog routes.
- Drop the AppFrame baselines-ready loading gate (user ruling: the bare
  status line reads worse than the shell's own pending rendering); both
  column occupants mount from first paint.

packages/client/ui-layout/src/client/AppFrame.tsx

@@ -85,12 +85,7 @@ export function AppFrame({
   useStore,
   actions,
   renderSlot,
-  useWorkspaces,
 }: AppFrameProps) {
-  // Baseline gate: before both object-layer baselines land, empty snapshots
-  // are indistinguishable from a genuine no-session state — rendering the
-  // conversation shell then would flash the New Workspace hero on boot.
-  const baselinesReady = useWorkspaces(s => s.baselinesReady)
   const panels = useStore((s) => s)
   const frameRef = useRef<HTMLDivElement | null>(null)
   const [viewport, setViewport] = useState(() => window.innerWidth)
@@ -156,24 +151,15 @@ export function AppFrame({
           width: cols.sidebar,
         })}
       </div>
-      {baselinesReady
-        ? (
-          <>
-            {/* Both column occupants stay at fixed tree positions. The
-                conversation is session-maybe; the strict details entry
-                naturally renders empty while no session is current. */}
-            <CenterColumn>{renderSlot('conversation', {})}</CenterColumn>
-            <DetailsColumn>{renderSlot('details', {})}</DetailsColumn>
-          </>
-          )
-        : (
-          <>
-            <CenterColumn>
-              <div role="status">Loading workspaces and sessions…</div>
-            </CenterColumn>
-            <DetailsColumn />
-          </>
-          )}
+      <>
+        {/* Both column occupants stay at fixed tree positions from first
+            paint — no loading gate (user ruling: the bare status line looked
+            worse than the shell's own pending rendering). The conversation
+            is session-maybe; the strict details entry naturally renders
+            empty while no session is current. */}
+        <CenterColumn>{renderSlot('conversation', {})}</CenterColumn>
+        <DetailsColumn>{renderSlot('details', {})}</DetailsColumn>
+      </>
       {/* The collapsed rail is fixed-width: no resize handle while closed. */}
       {panels.sidebar > 0 && <DragHandle side="sidebar" left={cols.sidebar} onStart={onSidebarStart} onDrag={onSidebarDrag} onEnd={onDragEnd} />}
       {cols.details > 0 && <DragHandle side="details" left={viewport - cols.details} onStart={onDetailsStart} onDrag={onDetailsDrag} onEnd={onDragEnd} />}