feat: add session management (rename, archive, delete)

Implements comprehensive session lifecycle management with user-friendly interactions:

Rename: Update session metadata.name via PATCH endpoint with conflict detection
Archive: Abort active sessions via DELETE endpoint with validation
Delete: Permanently remove inactive sessions with cascade cleanup

Backend:
- Store.deleteSession() removes session and cascade-deletes messages
- SyncEngine.renameSession() with concurrency error handling
- SyncEngine.deleteSession() with active session validation
- PATCH /sessions/:id for rename, DELETE /sessions/:id for delete

Frontend Components:
- RenameSessionDialog: Text input with auto-focus and error display
- SessionActionMenu: Modal with rename, archive, delete buttons
- ConfirmDialog: Reusable confirmation with error feedback
- SessionHeader: Menu button (⋮) triggering action menu
- SessionList: Long-press detection triggering item actions

Interactions:
- Long-press on session list items (500ms threshold) opens action menu
- Menu button in session header (non-Telegram environments only)
- Confirmation dialogs with descriptive warnings for destructive actions
- Real-time error display in dialogs on operation failure
- Haptic feedback on long-press via usePlatform hook

Accessibility:
- Keyboard support (Enter/Space) for long-press handler
- Focus management in RenameSessionDialog
- Proper ARIA labels and semantic HTML

web/src/hooks/mutations/useSessionActions.ts

@@ -25,6 +25,8 @@ export function useSessionActions(api: ApiClient | null, sessionId: string | nul
     switchSession: () => Promise<void>
     setPermissionMode: (mode: PermissionMode) => Promise<void>
     setModelMode: (mode: ModelMode) => Promise<void>
+    renameSession: (name: string) => Promise<void>
+    deleteSession: () => Promise<void>
     isPending: boolean
 } {
     const queryClient = useQueryClient()
@@ -75,11 +77,38 @@ export function useSessionActions(api: ApiClient | null, sessionId: string | nul
         onSuccess: () => void invalidateSession(),
     })
 
+    const renameMutation = useMutation({
+        mutationFn: async (name: string) => {
+            if (!api || !sessionId) {
+                throw new Error('Session unavailable')
+            }
+            await api.renameSession(sessionId, name)
+        },
+        onSuccess: () => void invalidateSession(),
+    })
+
+    const deleteMutation = useMutation({
+        mutationFn: async () => {
+            if (!api || !sessionId) {
+                throw new Error('Session unavailable')
+            }
+            await api.deleteSession(sessionId)
+        },
+        onSuccess: async () => {
+            if (!sessionId) return
+            queryClient.removeQueries({ queryKey: queryKeys.session(sessionId) })
+            queryClient.removeQueries({ queryKey: queryKeys.messages(sessionId) })
+            await queryClient.invalidateQueries({ queryKey: queryKeys.sessions })
+        },
+    })
+
     return {
         abortSession: abortMutation.mutateAsync,
         switchSession: switchMutation.mutateAsync,
         setPermissionMode: permissionMutation.mutateAsync,
         setModelMode: modelMutation.mutateAsync,
-        isPending: abortMutation.isPending || switchMutation.isPending || permissionMutation.isPending || modelMutation.isPending,
+        renameSession: renameMutation.mutateAsync,
+        deleteSession: deleteMutation.mutateAsync,
+        isPending: abortMutation.isPending || switchMutation.isPending || permissionMutation.isPending || modelMutation.isPending || renameMutation.isPending || deleteMutation.isPending,
     }
 }