* fix(acp): implicit streamToParent for mode=run without thread
When spawning ACP sessions with mode=run and no thread binding,
automatically route output to parent session instead of Discord.
This enables agent-to-agent supervision patterns where the spawning
agent wants results returned programmatically, not posted as chat.
The change makes sessions_spawn with runtime=acp and thread=false
behave like direct acpx invocation - output goes to the spawning
session, not to Discord.
Fixes the issue where mode=run without thread still posted to Discord
because hasDeliveryTarget was true when called from a Discord context.
* fix: use resolved spawnMode instead of params.mode
Move implicit streamToParent check to after resolveSpawnMode so that
both explicit mode="run" and omitted mode (which defaults to "run"
when thread is false) correctly trigger parent routing.
This fixes the issue where callers that rely on default mode selection
would not get the intended parent streaming behavior.
* fix: tighten implicit ACP parent relay gating (#42404) (thanks @davidguttman)
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Co-authored-by: Onur Solmaz <2453968+osolmaz@users.noreply.github.com>
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