fix: pass threadId/to/accountId from parent to subagent gateway call

When spawning a subagent, the requesterOrigin's threadId, to, and
accountId were not forwarded to the callGateway({method:'agent'}) params.
This meant the subagent's runContext had no currentThreadTs or
currentChannelId, so resolveTelegramAutoThreadId could not auto-inject
the forum topic thread ID when the subagent used the message tool.

Changes:
- sessions-spawn-tool: pass to, accountId, threadId from requesterOrigin
- run-context: populate currentChannelId from opts.to as fallback

Fixes subagent messages landing in General Topic instead of the correct
Telegram DM topic thread.

src/commands/agent/run-context.ts

@@ -42,5 +42,14 @@ export function resolveAgentRunContext(opts: AgentCommandOpts): AgentRunContext
     merged.currentThreadTs = String(opts.threadId);
   }
 
+  // Populate currentChannelId from the outbound target so that
+  // resolveTelegramAutoThreadId can match the originating chat.
+  if (!merged.currentChannelId && opts.to) {
+    const trimmedTo = opts.to.trim();
+    if (trimmedTo) {
+      merged.currentChannelId = trimmedTo;
+    }
+  }
+
   return merged;
 }