fix(desktop): don't let a named session.info rehome a fresh draft

`session.info` claimed the cwd for whatever the selection happened to be, so a
background tile's payload could re-point a fresh draft at the tile's workspace.

Treat a nonempty `stored_session_id` as non-matching when no primary session is
selected; only an ABSENT id uses the selected-session fallback (the backend
omits it on a lazy session, and refusing there would leave the workspace
un-owned for the rest of the conversation).

Matching goes through the lineage rather than raw string equality: the backend
id is the live session_key, which auto-compression rotates to the continuation
tip, while a selection made from a pinned row holds the stable lineage root.
Comparing those literally reads one conversation as two.

Co-authored-by: ZHJay <ZHJay@users.noreply.github.com>

apps/desktop/src/app/session/hooks/use-message-stream/gateway-event.ts

@@ -47,6 +47,8 @@ import {
   $currentCwd,
   $currentModel,
   $currentProvider,
+  $selectedStoredSessionId,
+  $sessions,
   sessionMatchesStoredId,
   setCurrentBranch,
   setCurrentCwd,
@@ -58,6 +60,7 @@ import {
   setMessages,
   setSessions,
   setTurnStartedAt,
+  setWorkspaceCwdOwner,
   setYoloActive
 } from '@/store/session'
 import { dropSessionState } from '@/store/session-states'
@@ -81,6 +84,42 @@ function firstBillingLine(text: string): string {
   return (text || '').split('\n')[0]?.trim() ?? ''
 }
 
+/**
+ * Whether a `session.info` payload's `stored_session_id` may be treated as the
+ * selected conversation's, so its cwd can be claimed for it (#71254).
+ *
+ * Absent is not the same as different: the backend omits the id on a
+ * not-yet-built (`lazy`) session, and refusing there would leave the workspace
+ * marked un-owned for the rest of the conversation. Matching goes through the
+ * lineage (`sessionMatchesStoredId`) so a compression-rotated tip and the root
+ * a pinned-row selection may hold still read as one conversation.
+ */
+function sessionInfoDescribesSelectedSession(storedSessionId: string | undefined): boolean {
+  const infoStoredSessionId = storedSessionId?.trim() || null
+  const selected = $selectedStoredSessionId.get() ?? null
+
+  if (!infoStoredSessionId) {
+    return true
+  }
+
+  // A named session cannot describe a fresh draft. Treating a null selection as
+  // a wildcard let a background tile's `session.info` rehome the draft to the
+  // tile's workspace.
+  if (!selected) {
+    return false
+  }
+
+  if (infoStoredSessionId === selected) {
+    return true
+  }
+
+  // Either id may be the live tip or the lineage root, so ask whether ONE row
+  // answers to both rather than assuming which side rotated.
+  return $sessions
+    .get()
+    .some(session => sessionMatchesStoredId(session, infoStoredSessionId) && sessionMatchesStoredId(session, selected))
+}
+
 /**
  * A turn failed on a billing wall (out of credits / payment required). The
  * gateway forwards the structured descriptor built by `agent/billing_links.py`;
@@ -396,7 +435,7 @@ export function useGatewayEventHandler(deps: GatewayEventDeps) {
           // Active-session model/provider still flows through the session state
           // cache via updateSessionState → syncRuntimeMetadataToView below.
 
-          if (typeof payload?.cwd === 'string') {
+          if (typeof payload?.cwd === 'string' && sessionInfoDescribesSelectedSession(payload.stored_session_id)) {
             // The active session's agent can relocate itself (new repo/worktree
             // via the terminal). When the SAME active session's cwd actually
             // moves, follow it — refresh the project tree + scope so the sidebar
@@ -408,6 +447,14 @@ export function useGatewayEventHandler(deps: GatewayEventDeps) {
             lastCwdInfoSessionRef.current = sessionId
             setCurrentCwd(payload.cwd)
 
+            // The backend just confirmed the selected conversation's real
+            // workspace, so it owns the path we wrote. Without the claim the
+            // marker keeps naming whoever held it before — including the
+            // released state a detached resume leaves behind — and the primary
+            // workspace-derived surfaces stay hidden against a folder the
+            // backend has confirmed (#71254).
+            setWorkspaceCwdOwner($selectedStoredSessionId.get())
+
             if (cwdMoved && sameSession) {
               void followActiveSessionCwd(payload.cwd)
             }