feat: persist session origin metadata across connectors

docs/concepts/session.md

@@ -25,6 +25,7 @@ All session state is **owned by the gateway** (the “master” Clawdbot). UI cl
 - Transcripts: `~/.clawdbot/agents/<agentId>/sessions/<SessionId>.jsonl` (Telegram topic sessions use `.../<SessionId>-topic-<threadId>.jsonl`).
 - The store is a map `sessionKey -> { sessionId, updatedAt, ... }`. Deleting entries is safe; they are recreated on demand.
 - Group entries may include `displayName`, `channel`, `subject`, `room`, and `space` to label sessions in UIs.
+- Session entries include `origin` metadata (label + routing hints) so UIs can explain where a session came from.
 - Clawdbot does **not** read legacy Pi/Tau session folders.
 
 ## Session pruning
@@ -113,3 +114,11 @@ Send these as standalone messages so they register.
 ## Tips
 - Keep the primary key dedicated to 1:1 traffic; let groups keep their own keys.
 - When automating cleanup, delete individual keys instead of the whole store to preserve context elsewhere.
+
+## Session origin metadata
+Each session entry records where it came from (best-effort) in `origin`:
+- `label`: human label (resolved from conversation label + group subject/channel)
+- `provider`: normalized channel id (including extensions)
+- `from`/`to`: raw routing ids from the inbound envelope
+- `accountId`: provider account id (when multi-account)
+- `threadId`: thread/topic id when the channel supports it