fix(gateway): relay TTS attachments + semantic auto-thread rename on the title turn

[benbarclay]

Relay TTS attachments + semantic auto-thread rename on the title turn

Two relay-lane bugs from live Discord staging testing (2026-07-29), one PR because both close manual-test findings on the same lane.

1 · TTS audio never attached over relay

Symptom: text_to_speech succeeded (tool result carried media_tag), the reply text arrived, but no audio attachment — on any relay platform.

Root cause (from fly logs + transcript on the staging box): _history_media_paths_for_session builds the delivered-media dedup set from the persisted transcript, excluding only the trailing assistant entry. But the agent persists rows as it produces them — by delivery time the current turn's TTS tool result was already in the transcript, so the fresh TTS path deduped against itself and the attachment was silently stripped. Log signature (exact staging hit, 14:37:50 & 14:40:34): response_delivery_dropped: non-empty response (58 chars) produced no delivered message or attachment … (empty after extract, recovery yielded nothing) — 58 chars = the bare MEDIA: tag.

Fix: exclude everything from the last user message onward (the whole current turn) from the dedup set; prior-turn dedup unchanged; no-user-row stores keep the old trailing-assistant fallback. Affects the non-streaming delivery path on every adapter (native + relay) — the streaming path passes explicit history and was unaffected.

2 · Auto-created threads never got the LLM session-title rename

Symptom: initial thread title fine; semantic rename (auto session title → thread name) never happened. Staging telemetry: zero thread_rename ops ever sent.

Root cause: the auto-title fires on the first exchange, whose source is the parent-channel event — the thread didn't exist at ingest, so the Phase 4 auto-thread markers can't be present and _is_discord_auto_thread_lane never matches on the relay title turn. (Marker path works for turn-2+ events inside the thread — the title turn is exactly the turn it can't cover.)

Fix: consume the connector's new send-result feedback (paired NousResearch/gateway-gateway#188 — contract §SendResult thread_id/auto_thread_name, additive): RelayAdapter.send() caches (thread_id, initial_name) per chat (bounded 256); run.py's title-callback registration + rename lane read it back, passing initial_name as only_if_current_name so the human-rename-wins guard holds over relay too. Native marker path unchanged; connectors that don't stamp the fields degrade to exactly the old behavior.

Tests

• test_relay_threads.py +3: feedback capture, absence, bound (relay suite 144 passed)
• test_history_media_current_turn.py (new, 3): current-turn TTS not deduped · prior-turn still deduped · no-user-row fallback

ruff + Windows-footguns clean. No ops flags; no env changes.