feat(chat): add local-first conversation workspace

chat/lib/import-title-template.ts

@@ -0,0 +1,32 @@
+export type ImportTitleContext = {
+  title: string;
+  format: string;
+  file: string;
+  folder: string;
+  date: string;
+  model: string;
+  provider: string;
+  index: number;
+};
+
+const placeholders = new Set(["title", "format", "file", "folder", "date", "model", "provider", "index"]);
+
+export function applyImportTitleTemplate(template: string, context: ImportTitleContext) {
+  const source = template.trim() || "{title}";
+  const unknown = [...source.matchAll(/\{([^{}]+)\}/g)]
+    .map((match) => match[1])
+    .filter((name) => !placeholders.has(name));
+  if (unknown.length) throw new Error(`未知标题变量：${[...new Set(unknown)].map((name) => `{${name}}`).join("、")}`);
+  const values: Record<string, string> = {...context, index: String(context.index)};
+  const rendered = source.replace(/\{([^{}]+)\}/g, (match, name) => values[name] ?? match).trim();
+  return rendered || context.title.trim() || "导入的会话";
+}
+
+export function importFileStem(filename: string) {
+  return filename.replace(/\.xiteng-chat\.json$/i, "").replace(/\.(?:jsonl|json)$/i, "");
+}
+
+export function importSourceFolder(source: string) {
+  const parts = source.replaceAll("\\", "/").split("/").map((part) => part.trim()).filter(Boolean);
+  return parts.length > 1 ? parts.at(-2)! : "";
+}