feat(ext/shared): message types for LastPass import

Adds parse_lastpass_csv (preview) and import_lastpass_commit
(write) to the popup-only message set, plus typed response
helpers. SW handlers + UI follow in Tasks 12-14.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

extension/src/shared/messages.ts

@@ -55,7 +55,9 @@ export type PopupMessage =
       bytes: ArrayBuffer;
       passphrase: string;
       newRemote: { hostType: 'gitea' | 'github'; hostUrl: string; repoPath: string; apiToken: string };
-    };
+    }
+  | { type: 'parse_lastpass_csv'; bytes: ArrayBuffer }
+  | { type: 'import_lastpass_commit'; items: Item[] };
 
 // --- Messages a content script may send ---
 
@@ -161,6 +163,7 @@ export const POPUP_ONLY_TYPES: ReadonlySet<PopupMessage['type']> = new Set([
   'get_field_history',
   'get_session_config', 'update_session_config',
   'export_backup', 'restore_backup',
+  'parse_lastpass_csv', 'import_lastpass_commit',
 ] as PopupMessage['type'][]);
 
 export interface ExportBackupResponse extends Extract<Response, { ok: true }> {
@@ -173,6 +176,19 @@ export interface RestoreBackupResponse extends Extract<Response, { ok: true }> {
   };
 }
 
+export interface ParseLastPassCsvResponse extends Extract<Response, { ok: true }> {
+  data: {
+    items: Item[];
+    warnings: Array<{ row: number; title?: string; message: string }>;
+  };
+}
+
+export interface ImportLastPassCommitResponse extends Extract<Response, { ok: true }> {
+  data: {
+    summary: { itemCount: number };
+  };
+}
+
 export const CONTENT_CALLABLE_TYPES: ReadonlySet<ContentMessage['type']> = new Set([
   'get_autofill_candidates', 'get_credentials', 'check_credential', 'blacklist_site',
   'capture_save_login',