fix(telegram): support forum topics

Co-authored-by: Daniel Griesser <HazAT@users.noreply.github.com>
Co-authored-by: Nacho Iacovino <nachoiacovino@users.noreply.github.com>
Co-authored-by: Randy Ventures <RandyVentures@users.noreply.github.com>

docs/concepts/provider-routing.md

@@ -16,6 +16,7 @@ Goal: deterministic replies per provider, while supporting multi-agent + multi-a
 - **Canonical direct session (per agent):** direct chats collapse to `agent:<agentId>:<mainKey>` (default `main`). Groups/channels stay isolated per agent:
   - group: `agent:<agentId>:<provider>:group:<id>`
   - channel/room: `agent:<agentId>:<provider>:channel:<id>`
+  - Telegram forum topics: `agent:<agentId>:telegram:group:<chatId>:topic:<threadId>`
 - **Session store:** per-agent store lives under `~/.clawdbot/agents/<agentId>/sessions/sessions.json` (override via `session.store` with `{agentId}` templating). JSONL transcripts live next to it.
 - **WebChat:** attaches to the selected agent’s main session (so desktop reflects cross-provider history for that agent).
 - **Implementation hints:**