feat(webui): add initial webui with websocket chat flow

webui/src/lib/api.ts

@@ -0,0 +1,93 @@
+import type { ChatSummary } from "./types";
+
+export class ApiError extends Error {
+  status: number;
+  constructor(status: number, message: string) {
+    super(message);
+    this.status = status;
+    this.name = "ApiError";
+  }
+}
+
+async function request<T>(
+  url: string,
+  token: string,
+  init?: RequestInit,
+): Promise<T> {
+  const res = await fetch(url, {
+    ...(init ?? {}),
+    headers: {
+      ...(init?.headers ?? {}),
+      Authorization: `Bearer ${token}`,
+    },
+    credentials: "same-origin",
+  });
+  if (!res.ok) {
+    throw new ApiError(res.status, `HTTP ${res.status}`);
+  }
+  return (await res.json()) as T;
+}
+
+function splitKey(key: string): { channel: string; chatId: string } {
+  const idx = key.indexOf(":");
+  if (idx === -1) return { channel: "", chatId: key };
+  return { channel: key.slice(0, idx), chatId: key.slice(idx + 1) };
+}
+
+export async function listSessions(
+  token: string,
+  base: string = "",
+): Promise<ChatSummary[]> {
+  type Row = {
+    key: string;
+    created_at: string | null;
+    updated_at: string | null;
+    preview?: string;
+  };
+  const body = await request<{ sessions: Row[] }>(
+    `${base}/api/sessions`,
+    token,
+  );
+  return body.sessions.map((s) => ({
+    key: s.key,
+    ...splitKey(s.key),
+    createdAt: s.created_at,
+    updatedAt: s.updated_at,
+    preview: s.preview ?? "",
+  }));
+}
+
+export async function fetchSessionMessages(
+  token: string,
+  key: string,
+  base: string = "",
+): Promise<{
+  key: string;
+  created_at: string | null;
+  updated_at: string | null;
+  messages: Array<{
+    role: string;
+    content: string;
+    timestamp?: string;
+    tool_calls?: unknown;
+    tool_call_id?: string;
+    name?: string;
+  }>;
+}> {
+  return request(
+    `${base}/api/sessions/${encodeURIComponent(key)}/messages`,
+    token,
+  );
+}
+
+export async function deleteSession(
+  token: string,
+  key: string,
+  base: string = "",
+): Promise<boolean> {
+  const body = await request<{ deleted: boolean }>(
+    `${base}/api/sessions/${encodeURIComponent(key)}/delete`,
+    token,
+  );
+  return body.deleted;
+}