fix(telegram): pass parentPeer for forum topic binding inheritance (#9789)

Fixes #9545 and #9351.

When a message comes from a Telegram forum topic, the peer ID includes
the topic suffix (e.g., `-1001234567890:topic:99`). Users configure
bindings with the base group ID, which previously did not match.

This adds `parentPeer` to `resolveAgentRoute()` calls for forum groups,
enabling binding inheritance from the parent group to all topics.

- Extract `buildTelegramParentPeer()` helper in bot/helpers.ts
- Pass parentPeer in bot-message-context.ts, bot-handlers.ts,
  bot-native-commands.ts, and bot.ts (reaction handler)
- Add tests for forum topic routing and topic precedence

src/telegram/bot/helpers.ts

@@ -99,6 +99,24 @@ export function buildTelegramGroupFrom(chatId: number | string, messageThreadId?
   return `telegram:group:${buildTelegramGroupPeerId(chatId, messageThreadId)}`;
 }
 
+/**
+ * Build parentPeer for forum topic binding inheritance.
+ * When a message comes from a forum topic, the peer ID includes the topic suffix
+ * (e.g., `-1001234567890:topic:99`). To allow bindings configured for the base
+ * group ID to match, we provide the parent group as `parentPeer` so the routing
+ * layer can fall back to it when the exact peer doesn't match.
+ */
+export function buildTelegramParentPeer(params: {
+  isGroup: boolean;
+  resolvedThreadId?: number;
+  chatId: number | string;
+}): { kind: "group"; id: string } | undefined {
+  if (!params.isGroup || params.resolvedThreadId == null) {
+    return undefined;
+  }
+  return { kind: "group", id: String(params.chatId) };
+}
+
 export function buildSenderName(msg: Message) {
   const name =
     [msg.from?.first_name, msg.from?.last_name].filter(Boolean).join(" ").trim() ||