fix: refresh Telegram DM topic binding after session split (#20470)

[vominh1919]

Fixes #20470

Problem

When a session bound to a Telegram DM topic splits during mid-turn context compression, the gateway updates session_store._entries with the new session ID but does not update the corresponding row in telegram_dm_topic_bindings. On the next inbound message in that topic, the gateway reads the stale binding, calls switch_session() back to the pre-compression root session, reloads its full transcript, fires preflight compression, splits again — repeat forever.

Symptom: every message in a Telegram DM topic prints 📦 Preflight compression: ~N tokens >= threshold even after the conversation has been compressed multiple times. Each turn pays the full compression latency before any real work begins.

Fix

After session_store._save() updates the in-memory entry and persists it, call _record_telegram_topic_binding(source, entry) to also refresh the SQLite topic-binding row. The call is wrapped in try/except to guard against edge cases where bind_telegram_topic might raise (e.g. if the new session ID is already linked to a different topic).

_record_telegram_topic_binding already early-returns when source.thread_id is falsy, so this is safe across all platform surfaces — only Telegram DM topic bindings are affected.

Before vs After

	Before	After
Topic binding after split	Points to pre-compression root session	Points to post-split child session
Preflight compression on next message	Triggers every time (infinite loop)	Skipped (child session is small)
Compression latency per turn	Full compression cost	Zero (no re-compression needed)

[alt-glitch]

Competing fix for #20470 — see also #20486 which extracts the logic into a _sync_session_split_entry helper method and adds a dedicated regression test.

[teknium1]

This looks implemented on current main by the later merged Telegram topic-binding fix. This is an automated hermes-sweeper review.

Evidence:

• gateway/run.py:2586 defines _sync_telegram_topic_binding(), which documents the stale Telegram topic binding / repeated preflight compression loop and safely refreshes the binding through _record_telegram_topic_binding().
• gateway/run.py:8491 updates session_entry.session_id, calls session_store._save(), then calls _sync_telegram_topic_binding(source, session_entry, reason="agent-result-compression"), matching this PR's requested behavior.
• gateway/run.py:7781 also adds read-path self-healing via SessionDB.get_compression_tip(), so existing stale bindings are advanced and rewritten on the next inbound message.
• tests/gateway/test_telegram_topic_mode.py:451 covers the stale parent-binding regression and asserts the binding row is rewritten to the compression child.
• The implementing commit is db96fc60d0d3dc3f9e95dc6541d8edcccb2f2171 (fix(gateway): keep Telegram topic bindings aligned with compression children (#34409)), contained in tag v2026.6.5.

Thanks for the original fix. The final mainline change covers the same #20470 failure mode and adds the self-heal path for already-stale rows, so this PR can be closed as implemented on main.