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/agents/tools/sessions-spawn-tool.ts

@@ -231,6 +231,10 @@ export function createSessionsSpawnTool(opts?: {
             message: task,
             sessionKey: childSessionKey,
             channel: requesterOrigin?.channel,
+            to: requesterOrigin?.to ?? undefined,
+            accountId: requesterOrigin?.accountId ?? undefined,
+            threadId:
+              requesterOrigin?.threadId != null ? String(requesterOrigin.threadId) : undefined,
             idempotencyKey: childIdem,
             deliver: false,
             lane: AGENT_LANE_SUBAGENT,