fix(ai): a pi turn finished on a tool call is a completion, not a failure

pi reports `stop_reason = "toolUse"` when a turn ends right after a tool
result — which is exactly how the plan approval panel and a completed goal
close out. The bridge mapped that to `Incomplete`, so every such turn raised
the red "needs attention" banner and marked the pane as a failed command,
even though nothing went wrong.

`toolUse` now maps to `Succeeded`; `length`, `error` and `aborted` keep their
meanings. Nothing changes on the pi side.

Verified: unit tests for the outcome table and the notification path now cover
the host-finished case (completion notification, non-failure); full
`cargo test -p nebula --bin pebrel` — 1754 passed.

nebula_app/src/ai_hook/native_tests.rs

@@ -2,7 +2,7 @@ use super::*;
 
 #[test]
 fn non_successful_turns_do_not_emit_a_completion_notification() {
-    for reason in ["error", "aborted", "length", "toolUse"] {
+    for reason in ["error", "aborted", "length"] {
         let payload = serde_json::json!({"kind":"done", "stop_reason":reason});
         let event = parse_remote_envelope(
             format!("nebula-hook/1 source=pi\n{payload}").as_bytes(),
@@ -25,6 +25,17 @@ fn non_successful_turns_do_not_emit_a_completion_notification() {
     )
     .unwrap();
     assert!(crate::notify::Notification::from_ai_hook(&event, None, false,).is_some());
+    // Host-finished turns (plan menu, completed goal) end on a tool call; they
+    // must notify like an ordinary completion, not as a failure.
+    let event = parse_remote_envelope(
+        b"nebula-hook/1 source=pi
+{\"kind\":\"done\",\"stop_reason\":\"toolUse\"}",
+        Some(1),
+    )
+    .unwrap();
+    let notification = crate::notify::Notification::from_ai_hook(&event, None, false)
+        .expect("host-finished turns notify like ordinary completions");
+    assert!(!notification.is_failure(), "a toolUse finish is not a failure");
 }
 #[test]
 fn pi_result_metadata_distinguishes_legacy_unknown_and_background_work() {
@@ -36,7 +47,7 @@ fn pi_result_metadata_distinguishes_legacy_unknown_and_background_work() {
         (",\"stop_reason\":\"error\"", AiTurnOutcome::Failed, AgentStatus::Idle, true),
         (",\"stop_reason\":\"aborted\"", AiTurnOutcome::Cancelled, AgentStatus::Idle, false),
         (",\"stop_reason\":\"length\"", AiTurnOutcome::Incomplete, AgentStatus::Idle, true),
-        (",\"stop_reason\":\"toolUse\"", AiTurnOutcome::Incomplete, AgentStatus::Idle, true),
+        (",\"stop_reason\":\"toolUse\"", AiTurnOutcome::Succeeded, AgentStatus::Done, true),
         (",\"stop_reason\":\"future\"", AiTurnOutcome::Unknown, AgentStatus::Idle, true),
         (",\"stop_reason\":null", AiTurnOutcome::Unknown, AgentStatus::Idle, true),
         (",\"stop_reason\":42", AiTurnOutcome::Unknown, AgentStatus::Idle, true),

nebula_app/src/ai_hook/protocol.rs

@@ -235,7 +235,11 @@ pub(super) fn parse_envelope(bytes: &[u8]) -> Option<AiHookEvent> {
             Some("stop") => AiTurnOutcome::Succeeded,
             Some("error") => AiTurnOutcome::Failed,
             Some("aborted") => AiTurnOutcome::Cancelled,
-            Some("length" | "toolUse") => AiTurnOutcome::Incomplete,
+            Some("length") => AiTurnOutcome::Incomplete,
+            // pi ends a turn with `toolUse` when the host or an extension closes it
+            // right after a tool result (the plan menu, a completed goal). That is a
+            // finished turn, not a truncated one, so it must not raise a failure.
+            Some("toolUse") => AiTurnOutcome::Succeeded,
             None if !payload.as_object()?.contains_key("stop_reason") => AiTurnOutcome::Unspecified,
             _ => AiTurnOutcome::Unknown,
         }

nebula_app/src/notify.rs

@@ -696,7 +696,6 @@ mod delivery_tests {
             ("unknown", Some(AiTurnOutcome::Unknown)),
             ("future", Some(AiTurnOutcome::Unknown)),
             ("length", Some(AiTurnOutcome::Incomplete)),
-            ("toolUse", Some(AiTurnOutcome::Incomplete)),
         ] {
             let event = pi_result(Some(reason), None);
             let notification = Notification::from_ai_hook(&event, None, false);
@@ -708,7 +707,7 @@ mod delivery_tests {
                 result => panic!("unexpected {reason} result: {result:?}"),
             }
         }
-        for reason in [None, Some("stop")] {
+        for reason in [None, Some("stop"), Some("toolUse")] {
             let mut payload = serde_json::json!({"kind": "done"});
             if let Some(reason) = reason {
                 payload["stop_reason"] = reason.into();
@@ -716,7 +715,10 @@ mod delivery_tests {
             let wire = format!("nebula-hook/1 source=pi\n{payload}");
             let event = crate::ai_hook::parse_remote_envelope(wire.as_bytes(), Some(1)).unwrap();
             let note = Notification::from_ai_hook(&event, None, false).unwrap();
-            assert_eq!(matches!(note, Notification::AiTurn { .. }), reason == Some("stop"));
+            assert_eq!(
+                matches!(note, Notification::AiTurn { .. }),
+                matches!(reason, Some("stop") | Some("toolUse"))
+            );
         }
     }