Root promotion: request_directory gains primary; granted folder can become the workspace

One-way, once, scratch-primary sessions only; consent card says workspace.
Live roots + shell repoint, persisted; engine rebuilds fully anchored after the turn.

surfaces/gui/src/App.tsx

@@ -751,7 +751,7 @@ export function App() {
           if (unattendedRef.current) break;
           setItems((p) => [
             ...p,
-            { kind: "dirreq", reason: d.reason || "", path: d.path || "", writable: !!d.writable },
+            { kind: "dirreq", reason: d.reason || "", path: d.path || "", writable: !!d.writable, primary: !!d.primary },
           ]);
           break;
         case "tool_requested":

surfaces/gui/src/components/DirectoryRequestCard.tsx

@@ -26,9 +26,19 @@ export function DirectoryRequestCard({
     <div className="dirreq-card">
       <div className="dirreq-head">
         <Icon name="folderPlus" size={16} className="ico" />
-        <span>The agent is requesting access to a folder</span>
+        <span>
+          {item.primary
+            ? "The agent asks to make a folder this session's workspace"
+            : "The agent is requesting access to a folder"}
+        </span>
       </div>
       {item.reason && <div className="dirreq-reason">“{item.reason}”</div>}
+      {item.primary && (
+        <div className="dirreq-reason">
+          Granting makes this folder the session's primary working directory (read-write);
+          the scratch directory stays available for temporary files and artifacts.
+        </div>
+      )}
       <div className="dirreq-pathrow">
         <input
           className="dirreq-path"
@@ -41,16 +51,22 @@ export function DirectoryRequestCard({
         </button>
       </div>
       <div className="dirreq-actions">
-        <label className="dirreq-access">
-          <input type="checkbox" checked={writable} onChange={(e) => setWritable(e.target.checked)} />
-          Allow writing (read-write)
-        </label>
+        {!item.primary && (
+          <label className="dirreq-access">
+            <input type="checkbox" checked={writable} onChange={(e) => setWritable(e.target.checked)} />
+            Allow writing (read-write)
+          </label>
+        )}
         <span className="spacer" />
         <button className="btn" onClick={() => onRespond(false)}>
           Decline
         </button>
-        <button className="btn primary" disabled={!path.trim()} onClick={() => onRespond(true, path.trim(), writable)}>
-          Grant access
+        <button
+          className="btn primary"
+          disabled={!path.trim()}
+          onClick={() => onRespond(true, path.trim(), item.primary ? true : writable)}
+        >
+          {item.primary ? "Make workspace" : "Grant access"}
         </button>
       </div>
     </div>

surfaces/gui/src/components/InboxItemCard.tsx

@@ -378,11 +378,19 @@ export function InboxItemCard({
             onClick={() =>
               onResolve(
                 item.id,
-                JSON.stringify({ granted: true, path: item.data?.path || "", writable: !!item.data?.writable }),
+                JSON.stringify({
+                  granted: true,
+                  path: item.data?.path || "",
+                  writable: item.data?.primary ? true : !!item.data?.writable,
+                }),
               )
             }
           >
-            {item.data?.path ? "Grant" : "Grant (no folder)"}
+            {item.data?.path
+              ? item.data?.primary
+                ? "Make workspace"
+                : "Grant"
+              : "Grant (no folder)"}
           </button>
           <button className={BTN_BORDERED} onClick={() => onResolve(item.id, JSON.stringify({ granted: false }))}>
             Deny

surfaces/gui/src/types.ts

@@ -144,6 +144,7 @@ export type Item =
       reason: string;
       path?: string;
       writable?: boolean;
+      primary?: boolean; // root promotion: the folder becomes the session's workspace
       resolved?: "granted" | "denied";
     }
   | {