Redo connection manager: Stacks, More options, drag & drop, WinSCP import

Folders become Stacks (connections.json v2, no v1 migration): collapsible
stack-first list, open-stack-in-tabs (first reuses a pristine tab), drag
connections between stacks. More... reveals a per-connection Local
directory applied to the other panel when local and untouched. Import
reads a WinSCP.ini export incl. deobfuscated passwords.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/shared/rpc.ts

@@ -1,6 +1,5 @@
 import type {
 	AppSettings,
-	ConnFolder,
 	ConnectionConfig,
 	ConnectionsFile,
 	EntryType,
@@ -8,6 +7,7 @@ import type {
 	Result,
 	SavedConnection,
 	SshConfigHost,
+	Stack,
 	TransferSnapshot,
 } from "./types";
 
@@ -67,8 +67,13 @@ export type AppRPC = {
 				response: Result<{ id: string }>;
 			};
 			deleteConnection: { params: { id: string }; response: Result };
-			upsertFolder: { params: { folder: ConnFolder }; response: Result<{ id: string }> };
-			deleteFolder: { params: { id: string }; response: Result };
+			upsertStack: { params: { stack: Stack }; response: Result<{ id: string }> };
+			deleteStack: { params: { id: string }; response: Result };
+			/** Native file picker + parse of a WinSCP.ini export into the store. */
+			importWinScp: {
+				params: Record<string, never>;
+				response: Result<{ connections: number; stacks: number; skipped: number }>;
+			};
 			getSshConfigHosts: {
 				params: Record<string, never>;
 				response: Result<{ hosts: SshConfigHost[] }>;