feat(openai): add chat streaming and model commands

- add /openai (/chatgpt) chat command using OpenAI Responses API (streaming + incremental edits)
- add /openAIListModels, /openAIGetModel, /openAISetModel
- introduce base Command class and migrate non-chat commands to it
- wire OpenAI client + env vars (OPENAI_API_KEY, OPENAI_MODEL)
- bump deps (@google/genai, systeminformation, @types/node) and add openai

src/commands/ollama-prompt.ts

@@ -1,4 +1,4 @@
-import {ChatCommand} from "../base/chat-command";
+import {Command} from "../base/command";
 import {Message} from "typescript-telegram-bot-api";
 import {abortOllamaRequest, bot, getOllamaRequest, ollama, ollamaRequests} from "../index";
 import {escapeMarkdownV2Text, logError, oldReplyToMessage, startIntervalEditor} from "../util/utils";
@@ -9,7 +9,7 @@ import {Cancel} from "../callback_commands/cancel";
 import {OllamaCancel} from "../callback_commands/ollama-cancel";
 import {MessageStore} from "../common/message-store";
 
-export class OllamaPrompt extends ChatCommand {
+export class OllamaPrompt extends Command {
     command = "ollamaPrompt";
     argsMode = "required" as const;