fix(tabs): clearer send_to_tab context to stop busy-wait + wrong-recipient replies

Two behavioral problems observed once the tools were usable:

1. The SENDER busy-waited for a reply (ran 'sleep 20' / polled) instead of
   ending its turn. Tool description, the delivery result text, and the
   system-prompt one-liner now say plainly: do not sleep/poll/run commands
   to wait; a reply arrives on its own in a later turn (or via read_tab in a
   future turn); keep working if there's other work, else end your turn.

2. The RECIPIENT replied to its OWN user in plain text instead of routing the
   answer back through send_to_tab. The provenance wrapper now states the
   message is from another AGENT (not your user), and that to reply you must
   use send_to_tab addressed to the sender's handle — and only if asked, since
   it may just be context. A plain text answer reaches only your own user.

Tests updated for the new wording.

1 files changed, 1 insertions, 1 deletions

diff --git a/packages/api/src/agent-manager.ts b/packages/api/src/agent-manager.ts
index 36a26f8..4264884 100644
--- a/packages/api/src/agent-manager.ts
+++ b/packages/api/src/agent-manager.ts
@@ -84,7 +84,7 @@ const TOOL_DESCRIPTIONS: Record<string, string> = {
 	youtube_transcribe:
 		"Fetch the transcript/subtitles for a YouTube video. Set background=true to start in the background and get a job_id for later retrieval.",
 	send_to_tab:
-		"Send a message to another tab (agent) by its short ID, as shown in the tab bar. Fire-and-forget: it queues/wakes the target and returns immediately without waiting for a reply. Use read_tab later to read the target's response.",
+		"Send a message to another tab (agent) by its short ID, as shown in the tab bar. Fire-and-forget: it queues/wakes the target and returns immediately without waiting for a reply. Do NOT sleep, poll, or run commands to wait — a reply arrives on its own in a later turn (or use read_tab in a future turn); if you are only waiting, end your turn.",
 	read_tab:
 		"Read another tab (agent)'s most recent completed response by its short ID. Returns a non-blocking snapshot; if the target is still running you get its previous completed turn. Use after send_to_tab to collect a reply.",
 };