feat: add conversationTitle to context enhancement

Pass inbound group titles into <dsh_im_source> without extra platform API lookups.
DingTalk uses conversationTitle; Telegram groups use chat.title.

src/channels/dingtalk/dingtalk-bridge.mjs

@@ -1001,6 +1001,7 @@ export class DingtalkHarnessBridge {
           channel: 'dingtalk',
           senderId: sender,
           senderName: message.senderNick,
+          conversationTitle: message.conversationTitle,
         }));
       }
       if (typeof this.#api.createAiCard === 'function'

src/channels/shared/context-enhancement.mjs

@@ -1,6 +1,6 @@
 // Shared by the Host and settings UI; keep this module browser-compatible.
 export const CONTEXT_ENHANCEMENT_FIELDS = Object.freeze([
-  'channel', 'conversationType', 'senderId', 'senderName', 'botId',
+  'channel', 'conversationType', 'senderId', 'senderName', 'conversationTitle', 'botId',
 ]);
 
 export const CONTEXT_ENHANCEMENT_GUIDANCE_MAX_LENGTH = 8_000;
@@ -36,7 +36,10 @@ const CHANNELS = new Set([
   'wecom', 'weixin', 'feishu', 'dingtalk', 'qq',
   'slack', 'telegram', 'discord', 'whatsapp',
 ]);
-const SOURCE_LIMITS = { channel: 16, conversationType: 6, senderId: 256, senderName: 256, botId: 128 };
+const SOURCE_LIMITS = {
+  channel: 16, conversationType: 6, senderId: 256, senderName: 256,
+  conversationTitle: 256, botId: 128,
+};
 const CONTROL_CHARACTERS = /[\u0000-\u001f\u007f-\u009f\u202a-\u202e\u2066-\u2069]/g;
 
 function invalidConfig(message) {
@@ -61,7 +64,7 @@ function validateContextEnhancementScope(input) {
     throw invalidConfig('群聊和私聊开关必须是布尔值。');
   }
   if (!Array.isArray(fields) || ![...fields].every((field) => CONTEXT_ENHANCEMENT_FIELDS.includes(field))) {
-    throw invalidConfig('来源字段只能选择已定义的五个字段。');
+    throw invalidConfig('来源字段只能选择已定义的六个字段。');
   }
   if (typeof guidance !== 'string' || guidance.length > CONTEXT_ENHANCEMENT_GUIDANCE_MAX_LENGTH) {
     throw invalidConfig(`增强提示词不得超过 ${CONTEXT_ENHANCEMENT_GUIDANCE_MAX_LENGTH} 个字符。`);
@@ -146,7 +149,9 @@ function sourceString(value, field) {
 
 function sourceBlock(snapshot, sourceFactory) {
   const { fields } = snapshot.config;
-  const needsSource = fields.some((field) => ['channel', 'senderId', 'senderName'].includes(field));
+  const needsSource = fields.some((field) => [
+    'channel', 'senderId', 'senderName', 'conversationTitle',
+  ].includes(field));
   const source = needsSource ? sourceFactory?.() : null;
   const projected = {};
   for (const field of fields) {

src/channels/shared/text-harness-bridge.mjs

@@ -678,6 +678,7 @@ export class TextHarnessBridge {
           channel: this.#descriptor.key,
           senderId,
           senderName: message.contextSource?.()?.senderName,
+          conversationTitle: message.contextSource?.()?.conversationTitle,
         }));
       }
       const { answer, artifacts = [] } = await askInWorkspaceSession({

src/channels/telegram/telegram-runtime.mjs

@@ -166,6 +166,7 @@ export function normalizeTelegramUpdate(update, {
       senderName: [message.from?.first_name, message.from?.last_name]
         .filter((value) => typeof value === 'string' && value.trim())
         .map((value) => value.trim()).join(' ') || message.from?.username,
+      conversationTitle: direct ? undefined : message.chat?.title,
     }),
     senderIsBot: message.from?.is_bot === true,
     kind: direct ? 'direct' : 'group',