fix(gateway): gate relay-only rename kwargs to the relay lane (#78487)

[WynnD]

What does this PR do?

Fixes #78487: native Discord auto-thread semantic renames were silently dying since the connector-guard refactor. gateway/run.py passes prefer_connector_created / parent_chat_id to rename_thread unconditionally, but the native Discord adapter's rename_thread only accepts only_if_current_name. Every native-lane rename raised TypeError, swallowed by the bare except Exception (debug-level log only) — the "rename result" log line never fires and threads keep their initial auto-thread name.

This PR takes the call-site gating approach (option 2 from the issue): the connector-owned kwargs are passed only on the relay lane; the native lane calls with only_if_current_name only.

Why this approach vs #78495

#78495 makes the native adapter silently accept/ignore the connector kwargs (single call-site preserved). This PR instead gates at the call site, keeping the native adapter's signature strict — a future relay/native mismatch will fail loudly at the boundary rather than being papered over by ignored parameters. Both approaches fix the bug; maintainers can pick or combine (the gating + adapter tolerance compose cleanly).

Changes Made

• gateway/run.py: branch the rename_thread call on use_connector_guard — relay lane keeps prefer_connector_created=True + parent_chat_id; native lane passes only only_if_current_name.
• tests/gateway/relay/test_native_lane_rename_kwargs.py: regression tests — (1) native lane receives no connector kwargs with the string guard intact, (2) signature-strict native adapter completes without TypeError, (3) relay lane keeps connector-guard behavior.

How to Test

./venv/bin/python -m pytest tests/gateway/relay/test_native_lane_rename_kwargs.py -v
# 3 passed

# Live: restart gateway, create a Discord auto-thread via the native lane,
# confirm "discord auto-thread rename result: ... applied=True" at INFO
# (previously the attempt line fired with no result line).

Checklist

• Code follows the project's style guidelines
• Tests added/updated and passing
• No new dependencies
• Bug fix verified against live native-lane Discord renames (gateway restarted with this patch; rename result lines present, no TypeError)

[alt-glitch]

This was generated by AI during triage.

Related to #78495: both fix #78487, but this PR gates relay-only kwargs at the call site while #78495 makes the native adapter accept them. Maintainers should choose the contract they prefer.