fix: rich messages follow-ups — reply_parameters, send latch, opt-in default

- Use reply_parameters per the sendRichMessage spec instead of the
  undocumented reply_to_message_id scalar (silently ignored -> reply
  anchor quietly dropped).
- Latch rich sends off after an endpoint-capability failure (old PTB /
  server without sendRichMessage) so every later reply doesn't pay a
  doomed extra roundtrip; per-message BadRequests do NOT latch.
- Default rich_messages to OFF (opt-in) while the day-old Bot API 10.1
  endpoint is validated live; revert the prompt-hint table guidance
  until the default flips on.
- Tests: reply_parameters shape, send-latch behavior, BadRequest
  non-latch; rich tests opt in explicitly via extra.

website/docs/user-guide/messaging/telegram.md

@@ -900,14 +900,14 @@ gateway:
 
 ## Rendering: Rich Messages, Tables and Link Previews
 
-**Rich Messages (Bot API 10.1).** Final replies are sent with Telegram's native [`sendRichMessage`](https://core.telegram.org/bots/api#sendrichmessage) using the agent's **raw markdown**, so tables, task lists, headings, nested blockquotes, collapsible `<details>`, footnotes/references, math/formulas, underline, sub/superscript, marked text, and anchors render natively — no client-side flattening. In DMs the live streaming preview also uses `sendRichMessageDraft`, so the animated draft matches the final rich message. This is **on by default**; disable it (forcing the legacy MarkdownV2 path below) per platform:
+**Rich Messages (Bot API 10.1).** When enabled, final replies are sent with Telegram's native [`sendRichMessage`](https://core.telegram.org/bots/api#sendrichmessage) using the agent's **raw markdown**, so tables, task lists, headings, nested blockquotes, collapsible `<details>`, footnotes/references, math/formulas, underline, sub/superscript, marked text, and anchors render natively — no client-side flattening. In DMs the live streaming preview also uses `sendRichMessageDraft`, so the animated draft matches the final rich message. This is **opt-in** (default off) while the new endpoint is validated; enable it per platform:
 
 ```yaml
 gateway:
   platforms:
     telegram:
       extra:
-        rich_messages: false
+        rich_messages: true
 ```
 
 The rich path is skipped automatically when content exceeds the 32,768-byte rich text limit, and any rejection from Telegram (unsupported endpoint on an older `python-telegram-bot`, parser error, oversized blocks/columns) **transparently falls back** to the MarkdownV2 path — your message is never lost. Transient/network errors are *not* silently re-sent (no duplicate final message).

website/i18n/zh-Hans/docusaurus-plugin-content-docs/current/user-guide/messaging/telegram.md

@@ -877,14 +877,14 @@ gateway:
 
 ## 渲染：富消息、表格和链接预览
 
-**富消息（Bot API 10.1）。** 最终回复通过 Telegram 原生的 [`sendRichMessage`](https://core.telegram.org/bots/api#sendrichmessage) 发送，使用 Agent 的**原始 markdown**，因此表格、任务列表、标题、嵌套引用块、可折叠的 `<details>`、脚注/引用、数学公式、下划线、上下标、高亮文本和锚点都能原生渲染——无需客户端展平。在私聊中，实时流式预览也使用 `sendRichMessageDraft`，因此动画草稿与最终的富消息保持一致。此功能**默认开启**；如需禁用（改用下方的旧版 MarkdownV2 路径），可按平台配置：
+**富消息（Bot API 10.1）。** 启用后，最终回复通过 Telegram 原生的 [`sendRichMessage`](https://core.telegram.org/bots/api#sendrichmessage) 发送，使用 Agent 的**原始 markdown**，因此表格、任务列表、标题、嵌套引用块、可折叠的 `<details>`、脚注/引用、数学公式、下划线、上下标、高亮文本和锚点都能原生渲染——无需客户端展平。在私聊中，实时流式预览也使用 `sendRichMessageDraft`，因此动画草稿与最终的富消息保持一致。此功能为**选择性启用**（默认关闭），在新端点经过验证期间需手动开启；可按平台配置：
 
 ```yaml
 gateway:
   platforms:
     telegram:
       extra:
-        rich_messages: false
+        rich_messages: true
 ```
 
 当内容超过 32,768 字节的富文本上限时，富消息路径会自动跳过；Telegram 的任何拒绝（较旧 `python-telegram-bot` 不支持该端点、解析错误、块/列过多）都会**透明回退**到 MarkdownV2 路径——消息绝不会丢失。瞬时/网络错误**不会**被静默重发（不会产生重复的最终消息）。