Add stable workspace IDs

Workspaces now use stable, unique IDs (10 hex chars) instead of deriving IDs from paths. This simplifies workspace renames from 150 lines of complex migration logic to ~60 lines of metadata updates.

## Core Changes

**Stable ID Generation:**
- Generate at workspace creation: `crypto.randomBytes(5).toString('hex')`
- Separate `id` (stable, immutable) from `name` (mutable, user-facing)
- Add symlinks for UX: `~/.cmux/src/<project>/<name>` → `<id>`

**Type System:**
- `WorkspaceMetadata`: Backend type with stable ID, no path field
- `WorkspaceMetadataWithPaths`: Frontend type with computed paths
- IPC layer enriches metadata with `stableWorkspacePath` and `namedWorkspacePath`

**Workspace Operations:**
- Create: Generate stable ID before creating worktree
- Rename: Update metadata + symlink only (ID unchanged, ~60 lines)
- Remove: Clean up worktree, session data, and symlinks

**Frontend Integration:**
- Build `pathToMetadata` map for lookups (handles both stable and legacy)
- Use map lookups instead of parsing workspace IDs from paths
- Support both new stable-ID workspaces and legacy name-based workspaces

## File Structure

```
# New workspace
~/.cmux/src/cmux/a1b2c3d4e5/          # Worktree (stable ID)
~/.cmux/src/cmux/feature-branch → a1b2c3d4e5  # Symlink
~/.cmux/sessions/a1b2c3d4e5/          # Session data

# Legacy workspace (unchanged)
~/.cmux/src/cmux/stable-ids/          # Worktree
~/.cmux/sessions/cmux-stable-ids/     # Session data
```

## Benefits

- **Instant renames**: No file moves, just metadata update
- **Simpler code**: Removed 90 lines of complex migration/rollback logic
- **Better UX**: Symlinks let users navigate by readable names
- **Stable references**: Chat history, config stay valid across renames
- **Future-proof**: Enables workspace aliases, templates, cross-project refs

## Testing

- ✅ 511 unit tests pass
- ✅ 8 rename integration tests pass
- ✅ 5 remove integration tests pass
- ✅ 13 E2E tests pass
- ✅ 9 new config unit tests

Author: ammar-agent

src/App.tsx

@@ -1,11 +1,12 @@
-import { useState, useEffect, useCallback, useRef } from "react";
+import { useState, useEffect, useCallback, useRef, useMemo } from "react";
 import styled from "@emotion/styled";
 import { Global, css } from "@emotion/react";
 import { GlobalColors } from "./styles/colors";
 import { GlobalFonts } from "./styles/fonts";
 import { GlobalScrollbars } from "./styles/scrollbars";
 import type { ProjectConfig } from "./config";
 import type { WorkspaceSelection } from "./components/ProjectSidebar";
+import type { WorkspaceMetadataWithPaths } from "./types/workspace";
 import { LeftSidebar } from "./components/LeftSidebar";
 import NewWorkspaceModal from "./components/NewWorkspaceModal";
 import { AIView } from "./components/AIView";
@@ -172,6 +173,17 @@ function AppInner() {
       onSelectedWorkspaceUpdate: setSelectedWorkspace,
     });
 
+  // Build path-to-metadata lookup map (handles both stable and legacy paths)
+  const pathToMetadata = useMemo(() => {
+    const map = new Map<string, WorkspaceMetadataWithPaths>();
+    for (const metadata of workspaceMetadata.values()) {
+      // Map both stable path (with ID) and named path (with name/legacy)
+      map.set(metadata.stableWorkspacePath, metadata);
+      map.set(metadata.namedWorkspacePath, metadata);
+    }
+    return map;
+  }, [workspaceMetadata]);
+
   // NEW: Sync workspace metadata with the stores
   const workspaceStore = useWorkspaceStoreRaw();
   const gitStatusStore = useGitStatusStoreRaw();
@@ -230,21 +242,13 @@ function AppInner() {
       const metadata = Array.from(workspaceMetadata.values()).find((ws) => ws.id === workspaceId);
 
       if (metadata) {
-        // Find project for this workspace
-        for (const [projectPath, projectConfig] of projects.entries()) {
-          const workspace = projectConfig.workspaces.find(
-            (ws) => ws.path === metadata.workspacePath
-          );
-          if (workspace) {
-            setSelectedWorkspace({
-              workspaceId: metadata.id,
-              projectPath,
-              projectName: metadata.projectName,
-              workspacePath: metadata.workspacePath,
-            });
-            break;
-          }
-        }
+        // Find project for this workspace (metadata now includes projectPath)
+        setSelectedWorkspace({
+          workspaceId: metadata.id,
+          projectPath: metadata.projectPath,
+          projectName: metadata.projectName,
+          workspacePath: metadata.stableWorkspacePath,
+        });
       }
     }
     // Only run on mount
@@ -329,8 +333,9 @@ function AppInner() {
         result.set(
           projectPath,
           config.workspaces.slice().sort((a, b) => {
-            const aMeta = workspaceMetadata.get(a.path);
-            const bMeta = workspaceMetadata.get(b.path);
+            // Look up metadata by workspace path (handles both stable and legacy paths)
+            const aMeta = pathToMetadata.get(a.path);
+            const bMeta = pathToMetadata.get(b.path);
             if (!aMeta || !bMeta) return 0;
 
             // Get timestamp of most recent user message (0 if never used)
@@ -354,7 +359,7 @@ function AppInner() {
       }
       return true;
     },
-    [projects, workspaceMetadata, workspaceRecency]
+    [projects, workspaceMetadata, workspaceRecency, pathToMetadata]
   );
 
   const handleNavigateWorkspace = useCallback(
@@ -382,7 +387,8 @@ function AppInner() {
       const targetWorkspace = sortedWorkspaces[targetIndex];
       if (!targetWorkspace) return;
 
-      const metadata = workspaceMetadata.get(targetWorkspace.path);
+      // Look up metadata by workspace path (handles both stable and legacy paths)
+      const metadata = pathToMetadata.get(targetWorkspace.path);
       if (!metadata) return;
 
       setSelectedWorkspace({
@@ -392,7 +398,7 @@ function AppInner() {
         workspaceId: metadata.id,
       });
     },
-    [selectedWorkspace, sortedWorkspacesByProject, workspaceMetadata, setSelectedWorkspace]
+    [selectedWorkspace, sortedWorkspacesByProject, pathToMetadata, setSelectedWorkspace]
   );
 
   // Register command sources with registry

src/components/LeftSidebar.tsx

@@ -1,7 +1,7 @@
 import React from "react";
 import styled from "@emotion/styled";
 import type { ProjectConfig } from "@/config";
-import type { WorkspaceMetadata } from "@/types/workspace";
+import type { WorkspaceMetadataWithPaths } from "@/types/workspace";
 import type { WorkspaceSelection } from "./ProjectSidebar";
 import type { Secret } from "@/types/secrets";
 import ProjectSidebar from "./ProjectSidebar";
@@ -21,7 +21,7 @@ const LeftSidebarContainer = styled.div<{ collapsed?: boolean }>`
 
 interface LeftSidebarProps {
   projects: Map<string, ProjectConfig>;
-  workspaceMetadata: Map<string, WorkspaceMetadata>;
+  workspaceMetadata: Map<string, WorkspaceMetadataWithPaths>;
   selectedWorkspace: WorkspaceSelection | null;
   onSelectWorkspace: (selection: WorkspaceSelection) => void;
   onAddProject: () => void;

src/components/ProjectSidebar.tsx

@@ -3,7 +3,7 @@ import { createPortal } from "react-dom";
 import styled from "@emotion/styled";
 import { css } from "@emotion/react";
 import type { ProjectConfig, Workspace } from "@/config";
-import type { WorkspaceMetadata } from "@/types/workspace";
+import type { WorkspaceMetadataWithPaths } from "@/types/workspace";
 import { usePersistedState } from "@/hooks/usePersistedState";
 import { DndProvider } from "react-dnd";
 import { HTML5Backend, getEmptyImage } from "react-dnd-html5-backend";
@@ -471,7 +471,7 @@ const ProjectDragLayer: React.FC = () => {
 
 interface ProjectSidebarProps {
   projects: Map<string, ProjectConfig>;
-  workspaceMetadata: Map<string, WorkspaceMetadata>;
+  workspaceMetadata: Map<string, WorkspaceMetadataWithPaths>;
   selectedWorkspace: WorkspaceSelection | null;
   onSelectWorkspace: (selection: WorkspaceSelection) => void;
   onAddProject: () => void;
@@ -512,6 +512,17 @@ const ProjectSidebarInner: React.FC<ProjectSidebarProps> = ({
   onUpdateSecrets,
   sortedWorkspacesByProject,
 }) => {
+  // Build path-to-metadata lookup map (handles both stable and legacy paths)
+  const pathToMetadata = React.useMemo(() => {
+    const map = new Map<string, WorkspaceMetadataWithPaths>();
+    for (const metadata of workspaceMetadata.values()) {
+      // Map both stable path (with ID) and named path (with name/legacy)
+      map.set(metadata.stableWorkspacePath, metadata);
+      map.set(metadata.namedWorkspacePath, metadata);
+    }
+    return map;
+  }, [workspaceMetadata]);
+
   // Workspace-specific subscriptions moved to WorkspaceListItem component
 
   // Store as array in localStorage, convert to Set for usage
@@ -822,7 +833,8 @@ const ProjectSidebarInner: React.FC<ProjectSidebarProps> = ({
                             </WorkspaceHeader>
                             {(sortedWorkspacesByProject.get(projectPath) ?? config.workspaces).map(
                               (workspace) => {
-                                const metadata = workspaceMetadata.get(workspace.path);
+                                // Look up metadata by workspace path (handles both stable ID paths and legacy name paths)
+                                const metadata = pathToMetadata.get(workspace.path);
                                 if (!metadata) return null;
 
                                 const workspaceId = metadata.id;
@@ -833,6 +845,7 @@ const ProjectSidebarInner: React.FC<ProjectSidebarProps> = ({
                                   <WorkspaceListItem
                                     key={workspace.path}
                                     workspaceId={workspaceId}
+                                    workspaceName={metadata.name}
                                     workspacePath={workspace.path}
                                     projectPath={projectPath}
                                     projectName={projectName}

src/components/WorkspaceListItem.tsx

@@ -10,12 +10,6 @@ import { ModelDisplay } from "./Messages/ModelDisplay";
 import { StatusIndicator } from "./StatusIndicator";
 import { useRename } from "@/contexts/WorkspaceRenameContext";
 
-// Helper function to extract workspace display name from path
-function getWorkspaceDisplayName(workspacePath: string): string {
-  const pathParts = workspacePath.split("/");
-  return pathParts[pathParts.length - 1] || "Unknown";
-}
-
 // Styled Components
 const WorkspaceStatusIndicator = styled(StatusIndicator)`
   margin-left: 8px;
@@ -134,6 +128,7 @@ export interface WorkspaceSelection {
 export interface WorkspaceListItemProps {
   // Minimal data - component accesses stores directly for the rest
   workspaceId: string;
+  workspaceName: string; // User-facing workspace name (from metadata)
   workspacePath: string;
   projectPath: string;
   projectName: string;
@@ -147,6 +142,7 @@ export interface WorkspaceListItemProps {
 
 const WorkspaceListItemInner: React.FC<WorkspaceListItemProps> = ({
   workspaceId,
+  workspaceName,
   workspacePath,
   projectPath,
   projectName,
@@ -167,7 +163,8 @@ const WorkspaceListItemInner: React.FC<WorkspaceListItemProps> = ({
   const [editingName, setEditingName] = useState<string>("");
   const [renameError, setRenameError] = useState<string | null>(null);
 
-  const displayName = getWorkspaceDisplayName(workspacePath);
+  // Use workspace name from metadata instead of deriving from path
+  const displayName = workspaceName;
   const isStreaming = sidebarState.canInterrupt;
   const streamingModel = sidebarState.currentModel;
   const isEditing = editingWorkspaceId === workspaceId;