fix(#1257): confirm delivery by draft transition, not prompt detection (adopts #1262) (#1332)

Co-authored-by: code-infra-01 <[email protected]>

packages/mosaic/framework/guides/FLEET-COMMS.md

@@ -53,21 +53,23 @@ sends, it does not auto-reply.
 
 ### Exit codes
 
-| rc  | Meaning                                        |
-| --- | ---------------------------------------------- |
-| 0   | delivered or queued                            |
-| 1   | target session not found                       |
-| 2   | text reached the pane but is **still a draft** |
-| 3   | usage error (bad class, missing `-s`)          |
+| rc  | Meaning                                                                                      |
+| --- | -------------------------------------------------------------------------------------------- |
+| 0   | delivered or queued                                                                          |
+| 1   | target session not found                                                                     |
+| 2   | submission unconfirmed: draft still on the input line, or no positive evidence of submission |
+| 3   | usage error (bad class, missing `-s`)                                                        |
 
-**Never retry on rc=2.** The message is in the target pane; retrying double-sends it. Confirm
-instead:
+**Never retry on rc=2.** The message may be in the target pane, and a retry can double-send it.
+Confirm instead:
 
 ```bash
 tmux capture-pane -p -t <session>:0.0 | tail -20
 ```
 
-rc=2 is the normal result when the target is an idle pi seat.
+rc=0 is the normal result for both idle and busy pi seats (submission confirmed by draft
+transition, not by prompt glyph). rc=2 on a healthy seat is exceptional — treat it as a real
+report and investigate the pane.
 
 ## Durable comms