fix: dedupe shared worktree ownership

Cherry-picked from claude branch 7b3bec48 (fix: dedupe shared worktree ownership and title sessions immediately).

Only the worktree-dedupe half applies to main: partitionWorktreesByRegisteredProject and its callers (SessionSidebar, ElectronMiniChatApp, MobileApp, MobileSessionsSheet) plus tests and sidebar docs.

The session-title half (title sessions immediately) remains on the claude branch: the session-title runtime and its claude-code transcript translator imports do not exist on main and cannot build there until the Claude harness lands.

packages/ui/src/components/session/SessionSidebar.tsx

@@ -47,7 +47,11 @@ import { SessionNodeItem } from './sidebar/SessionNodeItem';
 import type { SessionNodeRenderExtras } from './sidebar/sessionNodeItemUtils';
 import { useUpdateStore } from '@/stores/useUpdateStore';
 import { useShallow } from 'zustand/react/shallow';
-import { listProjectWorktrees, worktreeMapsEqual } from '@/lib/worktrees/worktreeManager';
+import {
+  listProjectWorktrees,
+  partitionWorktreesByRegisteredProject,
+  worktreeMapsEqual,
+} from '@/lib/worktrees/worktreeManager';
 import { checkIsGitRepository } from '@/lib/gitApi';
 import type { WorktreeMetadata } from '@/types/worktree';
 import type { SortableDragHandleProps } from './sidebar/sortableItems';
@@ -564,8 +568,8 @@ const SessionSidebarComponent: React.FC<SessionSidebarProps> = ({
         return;
       }
 
-      const currentByProject = useSessionUIStore.getState().availableWorktreesByProject;
-      const worktreesByProject = new Map(currentByProject);
+      const knownWorktreesByProject = useSessionUIStore.getState().availableWorktreesByProject;
+      const worktreesByProject = new Map(knownWorktreesByProject);
       const unresolvedProjectPaths = new Set<string>();
 
       // Constrain fanout: previously `Promise.all(projects.map(...))` could
@@ -618,16 +622,17 @@ const SessionSidebarComponent: React.FC<SessionSidebarProps> = ({
           worktreesByProject.delete(projectPath);
         }
       }
-      const allWorktrees = [...worktreesByProject.values()].flat();
+      const partitionedWorktreesByProject = partitionWorktreesByRegisteredProject(projectEntries, worktreesByProject);
+      const allWorktrees = [...partitionedWorktreesByProject.values()].flat();
       // Newly appearing worktrees sort to the top of their project's
       // worktree list (see worktreeFirstSeen.ts).
       recordWorktreesSeen(allWorktrees.map((worktree) => worktree.path), Date.now());
 
       // Skip update if nothing changed — see worktreeMapsEqual JSDoc.
-      if (!worktreeMapsEqual(worktreesByProject, currentByProject)) {
+      if (!worktreeMapsEqual(partitionedWorktreesByProject, knownWorktreesByProject)) {
         useSessionUIStore.setState({
           availableWorktrees: allWorktrees,
-          availableWorktreesByProject: worktreesByProject,
+          availableWorktreesByProject: partitionedWorktreesByProject,
         });
       }
       setUnresolvedWorktreeProjectPaths(unresolvedProjectPaths);

packages/ui/src/components/session/sidebar/DOCUMENTATION.md

@@ -13,6 +13,7 @@
 - Group-level PR-status polling/indicators and worktree-group drag-to-reorder were removed together with the worktree grouping level; `oc.sessions.groupOrder` is no longer read or written. Worktree PR/branch context lives in the Worktrees surface.
 - Root session menus can quickly create a worktree from the session directory's current branch and move the full session subtree there while idle.
 - Directory loading is demand-driven: the sidebar publishes one complete priority plan for all known project/worktree directories, while the sync layer owns bounded execution.
+- When multiple configured projects are checkouts of the same Git repository, exactly one project owns the shared worktree topology: the configured canonical primary root when present, otherwise the first configured source for that repository. Any worktree path that is also a configured project is omitted from subordinate worktree groups, so every directory has one sidebar location while remaining part of bootstrap demand.
 
 ## VS Code grouping