fix: review-bot findings on the provider-hosted shell

- Keep ConversationSession mounted for blank sessions (chrome-less) so the
  draft-persistence mirror stays bound in the hero; hero typing reaches the
  chat store again.
- Restore the baselines-ready gate in AppFrame: empty boot snapshots no
  longer flash the New Workspace hero before either baseline lands.
- Commit ordinary sends through the machine (send-committed event +
  Shell.commitSend): undo can no longer resurrect already-sent content on
  the default-sink path.
- Give the production InputMachine a real wall clock so the typing-run
  merge window actually expires.
- Coalesce concurrent connectWorkspace creates per workspace: the summary
  has no cwd until the host frame lands, so a second New Session inside
  that window minted a duplicate hidden blank session.

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

@@ -85,7 +85,12 @@ 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)
@@ -151,13 +156,24 @@ export function AppFrame({
           width: cols.sidebar,
         })}
       </div>
-      <>
-        {/* 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>
-      </>
+      {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 />
+          </>
+          )}
       {/* 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} />}

packages/client/ui-layout/tests/app-frame.spec.tsx

@@ -160,13 +160,11 @@ describe('AppFrame', () => {
     expect(slotCalls.map((c) => c.key)).toContain('conversation')
   })
 
-  it('renders both column occupants before baselines settle (no loading gate)', () => {
-    // The loading branch is gone: fixed tree positions from first paint, the
-    // occupants render their own pending states.
+  it('keeps the loading branch until both object-layer baselines are ready', () => {
     baselinesReady.current = false
-    const { slotCalls } = mountFrame()
-    expect(slotCalls.map((c) => c.key)).toContain('conversation')
-    expect(slotCalls.map((c) => c.key)).toContain('details')
+    const { slotCalls, getByRole } = mountFrame()
+    expect(getByRole('status').textContent).toContain('Loading workspaces and sessions')
+    expect(slotCalls.map((c) => c.key)).not.toContain('conversation')
   })
 
   it('sidebar slot receives live concession output as owner props', () => {