fix(ui): open saved plans against their owning project

Saved Project knowledge plans opened as an empty editor whenever the
viewer could not resolve the owning project from the current directory:
managed chats (openchamber:chats is not a registered project), worktrees
outside the repo path, and plan tabs restored after a reload. Titles
still rendered because the list reads the manifest through the correct
owner.

- Thread the owner explicitly (savedProjectPlan = { projectRef, planId })
  from the panel, mobile surfaces, and persisted context tabs; PlanView
  no longer guesses the project.
- An unrecognized directory resolves to no owner instead of borrowing
  the active project's knowledge.
- Serialize plan writes per document (planSaveQueue) so close/switch
  within the autosave debounce no longer drops the last edits, saves
  cannot land out of order, and a recovered save clears the error banner.
- Send saved-plan contents inline in Improve/Implement prompts (they
  have no file path); disable those actions for managed-chat plans,
  which have no project directory to create a session in.
- Drop persisted plan tabs that carry an id without an owner rather than
  reopening them against a guessed project.

packages/ui/src/apps/MobileApp.tsx

@@ -22,6 +22,7 @@ import { useUpdatePolling } from '@/hooks/useUpdatePolling';
 import { useWindowTitle } from '@/hooks/useWindowTitle';
 import { opencodeClient } from '@/lib/opencode/client';
 import type { RuntimeAPIs } from '@/lib/api/types';
+import type { ProjectRef } from '@/lib/projectContextApi';
 import { readTabletLayout, useOrientation, useTabletLayout } from '@/lib/device';
 import { useHardwareKeyboard } from '@/lib/hardwareKeyboard';
 import { useI18n } from '@/lib/i18n';
@@ -111,7 +112,7 @@ const MobileShell: React.FC<{ onActiveConnectionDeleted: () => void }> = ({ onAc
   const [workspaceTab, setWorkspaceTab] = React.useState<MobileWorkspaceTab>('changes');
   // A plan opened from the workspace drawer's Notes tab, shown as a fullscreen
   // layer on top of it (back returns to the notes).
-  const [openPlan, setOpenPlan] = React.useState<{ id: string; title: string } | null>(null);
+  const [openPlan, setOpenPlan] = React.useState<{ id: string; title: string; projectRef: ProjectRef } | null>(null);
   const [settingsInitialMobileStage, setSettingsInitialMobileStage] = React.useState<'nav' | 'page-content'>('nav');
   // When set, the Changes surface opens directly into the per-file diff for this path.
   const [pendingChangesDiff, setPendingChangesDiff] = React.useState<{ path: string; staged: boolean } | null>(null);
@@ -542,7 +543,7 @@ const MobileShell: React.FC<{ onActiveConnectionDeleted: () => void }> = ({ onAc
           >
             <ErrorBoundary>
               <PlanView
-                projectPlanId={openPlan.id}
+                savedProjectPlan={{ projectRef: openPlan.projectRef, planId: openPlan.id }}
                 onNavigatedToChat={() => {
                   closeSurface();
                   closeWorkspace();

packages/ui/src/apps/MobileWorkspaceDrawer.tsx

@@ -9,6 +9,7 @@ import { ErrorBoundary } from '@/components/ui/ErrorBoundary';
 import { SortableTabsStrip, type SortableTabsStripItem } from '@/components/ui/sortable-tabs-strip';
 import { TerminalView } from '@/components/views/TerminalView';
 import { useI18n } from '@/lib/i18n';
+import type { ProjectRef } from '@/lib/projectContextApi';
 import { cn } from '@/lib/utils';
 import { useDirectoryStore } from '@/stores/useDirectoryStore';
 import { useMcpConfigStore } from '@/stores/useMcpConfigStore';
@@ -105,7 +106,7 @@ export const MobileWorkspaceDrawer: React.FC<{
   /** When set, the Changes tab opens directly into the per-file diff. */
   pendingChangesDiff: { path: string; staged: boolean } | null;
   /** Notes tab: opens a plan fullscreen (layered above the drawer). */
-  onOpenPlan: (plan: { id: string; title: string }) => void;
+  onOpenPlan: (plan: { id: string; title: string; projectRef: ProjectRef }) => void;
   /** MCP tab: jump to the MCP settings page pre-seeded with a new server draft. */
   onOpenMcpSettings: () => void;
   variant?: 'drawer' | 'panel';