refactor(workspace): migrate from per-folder windows to single-window workspace

Replace the legacy folder + welcome routes with a unified /workspace route
that hosts all folders, conversations, tabs, and terminals in one window.

- Persist opened tabs to the database (opened_tabs entity + migration)
  so tab layout survives restarts and deep-link bootstrap restores state
- Replace FolderContext shim with AppWorkspaceProvider, ActiveFolderProvider,
  and TabProvider; expose both opened (folders) and full DB (allFolders)
  listings via list_all_folder_details
- Return conversations across all non-deleted folders from list_all when
  no folder filter is given, so the sidebar can show every folder's history
- Add ConversationContextBar above the chat input with folder picker
  (auto-opens unopened folders on select), branch picker, and commit /
  push / merge / stash entries to restore BranchDropdown functionality
- Rework sidebar with stats header, search, flat / folder-grouped view
  modes (localStorage-persisted), reveal-in-sidebar event subscriber,
  and per-folder context menu (focus, close tabs, remove from workspace);
  indent conversations under folder headers in grouped mode
- Gate terminal creation on active folder and show folder context
- Remove deprecated BranchDropdown, FolderNameDropdown, welcome route,
  and per-folder window commands
- Localize all new strings across 10 locales

src/components/layout/sidebar.tsx

@@ -1,9 +1,21 @@
 "use client"
 
-import { useCallback, useRef } from "react"
-import { ChevronsDownUp, ChevronsUpDown, Crosshair, Plus } from "lucide-react"
+import { useCallback, useEffect, useRef, useState } from "react"
+import {
+  ChevronsDownUp,
+  ChevronsUpDown,
+  Crosshair,
+  FolderPlus,
+  FolderTree,
+  Plus,
+  Rows3,
+  Search,
+  X,
+} from "lucide-react"
 import { useTranslations } from "next-intl"
-import { useFolderContext } from "@/contexts/folder-context"
+import { toast } from "sonner"
+import { useActiveFolder } from "@/contexts/active-folder-context"
+import { useAppWorkspace } from "@/contexts/app-workspace-context"
 import { useTabContext } from "@/contexts/tab-context"
 import { useSidebarContext } from "@/contexts/sidebar-context"
 import {
@@ -11,66 +23,213 @@ import {
   type SidebarConversationListHandle,
 } from "@/components/conversations/sidebar-conversation-list"
 import { Button } from "@/components/ui/button"
+import { Input } from "@/components/ui/input"
+import {
+  Tooltip,
+  TooltipContent,
+  TooltipProvider,
+  TooltipTrigger,
+} from "@/components/ui/tooltip"
 import { useIsMobile } from "@/hooks/use-mobile"
+import { isDesktop, openFileDialog } from "@/lib/platform"
+import {
+  loadSidebarViewMode,
+  saveSidebarViewMode,
+  type SidebarViewMode,
+} from "@/lib/sidebar-view-mode-storage"
+import { cn } from "@/lib/utils"
 
 export function Sidebar() {
   const t = useTranslations("Folder.sidebar")
-  const { folder } = useFolderContext()
+  const { activeFolder } = useActiveFolder()
+  const { allFolders, conversations, openFolder } = useAppWorkspace()
   const { openNewConversationTab } = useTabContext()
   const { isOpen, toggle } = useSidebarContext()
   const isMobile = useIsMobile()
   const listRef = useRef<SidebarConversationListHandle>(null)
 
+  const [viewMode, setViewMode] = useState<SidebarViewMode>("flat")
+  const [searchQuery, setSearchQuery] = useState("")
+
+  useEffect(() => {
+    // Hydrate from localStorage after mount to keep SSR/CSR markup consistent.
+    // eslint-disable-next-line react-hooks/set-state-in-effect
+    setViewMode(loadSidebarViewMode())
+  }, [])
+
+  const handleSetViewMode = useCallback((mode: SidebarViewMode) => {
+    setViewMode(mode)
+    saveSidebarViewMode(mode)
+  }, [])
+
+  useEffect(() => {
+    const onReveal = (e: Event) => {
+      const detail = (e as CustomEvent<{ folderId: number }>).detail
+      if (!detail) return
+      if (viewMode !== "grouped") {
+        setViewMode("grouped")
+        saveSidebarViewMode("grouped")
+      }
+      listRef.current?.revealFolder(detail.folderId)
+    }
+    window.addEventListener("sidebar:reveal-folder", onReveal)
+    return () => {
+      window.removeEventListener("sidebar:reveal-folder", onReveal)
+    }
+  }, [viewMode])
+
   const handleNewConversation = useCallback(() => {
-    if (!folder) return
-    openNewConversationTab(folder.path)
-  }, [folder, openNewConversationTab])
+    if (!activeFolder) return
+    openNewConversationTab(activeFolder.id, activeFolder.path)
+  }, [activeFolder, openNewConversationTab])
+
+  const handleOpenFolder = useCallback(async () => {
+    try {
+      if (!isDesktop()) {
+        toast.error(t("toasts.openFolderFailed"))
+        return
+      }
+      const result = await openFileDialog({
+        directory: true,
+        multiple: false,
+      })
+      if (!result) return
+      const selected = Array.isArray(result) ? result[0] : result
+      const detail = await openFolder(selected)
+      toast.success(t("toasts.folderOpened", { name: detail.name }))
+    } catch (err) {
+      console.error("[Sidebar] open folder failed:", err)
+      toast.error(t("toasts.openFolderFailed"))
+    }
+  }, [openFolder, t])
 
   if (!isOpen) return null
 
   return (
     <aside className="group/sidebar flex h-full min-h-0 flex-col overflow-hidden bg-sidebar text-sidebar-foreground select-none">
-      <div className="flex h-10 items-center justify-between border-b border-border px-4">
-        <h2 className="text-xs font-bold">{t("title")}</h2>
-        <div className="flex items-center gap-0.5 opacity-0 transition-opacity group-hover/sidebar:opacity-100">
-          <Button
-            variant="ghost"
-            size="icon"
-            className="h-6 w-6 shrink-0 text-muted-foreground"
-            onClick={() => listRef.current?.scrollToActive()}
-            title={t("locateActiveConversation")}
-          >
-            <Crosshair className="h-3.5 w-3.5" />
-          </Button>
-          <Button
-            variant="ghost"
-            size="icon"
-            className="h-6 w-6 shrink-0 text-muted-foreground"
-            onClick={() => listRef.current?.expandAll()}
-            title={t("expandAllGroups")}
-          >
-            <ChevronsUpDown className="h-3.5 w-3.5" />
-          </Button>
-          <Button
-            variant="ghost"
-            size="icon"
-            className="h-6 w-6 shrink-0 text-muted-foreground"
-            onClick={() => listRef.current?.collapseAll()}
-            title={t("collapseAllGroups")}
-          >
-            <ChevronsDownUp className="h-3.5 w-3.5" />
-          </Button>
-          <Button
-            variant="ghost"
-            size="icon"
-            className="h-6 w-6 shrink-0 text-muted-foreground"
-            onClick={handleNewConversation}
-            title={t("newConversation")}
-          >
-            <Plus className="h-3.5 w-3.5" />
-          </Button>
+      <TooltipProvider>
+        <div className="flex items-center justify-between border-b border-border px-3 py-2 gap-2">
+          <div className="flex items-center gap-2 min-w-0 text-[11px] text-muted-foreground tabular-nums">
+            <span className="truncate">
+              {t("statsLabel", {
+                folders: allFolders.length,
+                convos: conversations.length,
+              })}
+            </span>
+          </div>
+          <Tooltip>
+            <TooltipTrigger asChild>
+              <Button
+                variant="ghost"
+                size="icon"
+                className="h-6 w-6 shrink-0 text-muted-foreground"
+                onClick={handleOpenFolder}
+              >
+                <FolderPlus className="h-3.5 w-3.5" />
+              </Button>
+            </TooltipTrigger>
+            <TooltipContent side="bottom">{t("openFolder")}</TooltipContent>
+          </Tooltip>
         </div>
-      </div>
+
+        <div className="flex items-center gap-1 border-b border-border px-2 py-1.5">
+          <div className="relative flex-1 min-w-0">
+            <Search className="absolute left-2 top-1/2 -translate-y-1/2 h-3 w-3 text-muted-foreground pointer-events-none" />
+            <Input
+              value={searchQuery}
+              onChange={(e) => setSearchQuery(e.target.value)}
+              placeholder={t("searchPlaceholder")}
+              className="h-7 pl-6 pr-6 text-xs"
+            />
+            {searchQuery && (
+              <button
+                type="button"
+                onClick={() => setSearchQuery("")}
+                className="absolute right-1.5 top-1/2 -translate-y-1/2 text-muted-foreground hover:text-foreground rounded-sm p-0.5"
+              >
+                <X className="h-3 w-3" />
+              </button>
+            )}
+          </div>
+          <Tooltip>
+            <TooltipTrigger asChild>
+              <Button
+                variant="ghost"
+                size="icon"
+                className={cn(
+                  "h-7 w-7 shrink-0 text-muted-foreground",
+                  viewMode === "flat" && "bg-accent text-foreground"
+                )}
+                onClick={() => handleSetViewMode("flat")}
+              >
+                <Rows3 className="h-3.5 w-3.5" />
+              </Button>
+            </TooltipTrigger>
+            <TooltipContent side="bottom">{t("viewFlat")}</TooltipContent>
+          </Tooltip>
+          <Tooltip>
+            <TooltipTrigger asChild>
+              <Button
+                variant="ghost"
+                size="icon"
+                className={cn(
+                  "h-7 w-7 shrink-0 text-muted-foreground",
+                  viewMode === "grouped" && "bg-accent text-foreground"
+                )}
+                onClick={() => handleSetViewMode("grouped")}
+              >
+                <FolderTree className="h-3.5 w-3.5" />
+              </Button>
+            </TooltipTrigger>
+            <TooltipContent side="bottom">{t("viewGrouped")}</TooltipContent>
+          </Tooltip>
+        </div>
+
+        <div className="flex items-center justify-between border-b border-border px-2 h-7">
+          <h2 className="text-xs font-bold text-muted-foreground truncate">
+            {t("title")}
+          </h2>
+          <div className="flex items-center gap-0.5 opacity-0 transition-opacity group-hover/sidebar:opacity-100">
+            <Button
+              variant="ghost"
+              size="icon"
+              className="h-6 w-6 shrink-0 text-muted-foreground"
+              onClick={() => listRef.current?.scrollToActive()}
+              title={t("locateActiveConversation")}
+            >
+              <Crosshair className="h-3.5 w-3.5" />
+            </Button>
+            <Button
+              variant="ghost"
+              size="icon"
+              className="h-6 w-6 shrink-0 text-muted-foreground"
+              onClick={() => listRef.current?.expandAll()}
+              title={t("expandAllGroups")}
+            >
+              <ChevronsUpDown className="h-3.5 w-3.5" />
+            </Button>
+            <Button
+              variant="ghost"
+              size="icon"
+              className="h-6 w-6 shrink-0 text-muted-foreground"
+              onClick={() => listRef.current?.collapseAll()}
+              title={t("collapseAllGroups")}
+            >
+              <ChevronsDownUp className="h-3.5 w-3.5" />
+            </Button>
+            <Button
+              variant="ghost"
+              size="icon"
+              className="h-6 w-6 shrink-0 text-muted-foreground"
+              onClick={handleNewConversation}
+              disabled={!activeFolder}
+              title={t("newConversation")}
+            >
+              <Plus className="h-3.5 w-3.5" />
+            </Button>
+          </div>
+        </div>
+      </TooltipProvider>
 
       {/* On mobile, clicking a conversation card auto-closes the Sheet */}
       <div
@@ -86,7 +245,11 @@ export function Sidebar() {
             : undefined
         }
       >
-        <SidebarConversationList ref={listRef} />
+        <SidebarConversationList
+          ref={listRef}
+          viewMode={viewMode}
+          searchQuery={searchQuery}
+        />
       </div>
     </aside>
   )