fix(service): surface a service core that stopped for good

When the service watchdog gave up or the core vanished, the owner
monitor marked the core stopped without telling the user, and on macOS
left the system proxy on the dead mixed port (#8029).

- On SameOwnerFailure, clear the proxy through the helper while the
  session is still ours; displaced or unreachable owners still leave the
  machine-wide setting alone.
- Retain the stop as a core failure with its own message, recorded
  under the lifecycle lock and shown now or on next focus; a running
  core resets the notice dedup.
- Log each watchdog restart the service reports, since launchd discards
  the service's own log.

src-tauri/src/core/manager/mod.rs

@@ -74,6 +74,14 @@ impl fmt::Display for RunningMode {
     }
 }
 
+/// Why the Core is not running, kept until a Core starts again.
+#[derive(Clone, Debug, serde::Serialize, PartialEq, Eq)]
+#[serde(tag = "kind", content = "detail", rename_all = "camelCase")]
+pub enum CoreFailure {
+    StartFailed(String),
+    ServiceCoreStopped(String),
+}
+
 #[derive(Debug)]
 pub struct CoreManager {
     /// The Run State this manager reports transitions to.
@@ -87,7 +95,7 @@ pub struct CoreManager {
     job_handle: ArcSwapOption<OwnedHandle>,
     config_update_in_progress: AtomicBool,
     core_readiness_state: AtomicU64,
-    startup_error: parking_lot::Mutex<Option<String>>,
+    startup_error: parking_lot::Mutex<Option<CoreFailure>>,
     sidecar_exit: tokio::sync::Mutex<Option<tokio::task::JoinHandle<()>>>,
     // 串行化 start/stop/restart 和 sidecar→service 交接。
     // 锁序固定为 config_update_in_progress → lifecycle_lock。
@@ -143,14 +151,14 @@ impl CoreManager {
         self.run_state.mode_arc()
     }
 
-    pub(crate) fn record_startup_error(&self, error: String) {
+    pub(crate) fn record_startup_error(&self, failure: CoreFailure) {
         let mut startup_error = self.startup_error.lock();
         if matches!(*self.get_running_mode(), RunningMode::NotRunning) {
-            *startup_error = Some(error);
+            *startup_error = Some(failure);
         }
     }
 
-    pub(crate) fn get_startup_error(&self) -> Option<String> {
+    pub(crate) fn get_startup_error(&self) -> Option<CoreFailure> {
         self.startup_error.lock().clone()
     }
 
@@ -325,13 +333,13 @@ singleton!(CoreManager, CORE_MANAGER);
 
 #[cfg(test)]
 mod startup_error_tests {
-    use super::{CoreManager, RunningMode};
+    use super::{CoreFailure, CoreManager, RunningMode};
 
     #[test]
     fn recovery_invalidates_an_unread_startup_error_even_after_a_later_exit() {
         for mode in [RunningMode::Sidecar, RunningMode::Service] {
             let manager = CoreManager::isolated();
-            manager.record_startup_error("startup failed".into());
+            manager.record_startup_error(CoreFailure::StartFailed("startup failed".into()));
             manager.core_started(mode);
             manager.core_stopped();
             assert_eq!(manager.get_startup_error(), None);
@@ -341,9 +349,10 @@ mod startup_error_tests {
     #[test]
     fn unresolved_startup_error_survives_repeated_reads() {
         let manager = CoreManager::isolated();
-        manager.record_startup_error("startup failed".into());
+        let failure = CoreFailure::StartFailed("startup failed".into());
+        manager.record_startup_error(failure.clone());
         for _ in 0..2 {
-            assert_eq!(manager.get_startup_error().as_deref(), Some("startup failed"));
+            assert_eq!(manager.get_startup_error().as_ref(), Some(&failure));
         }
     }
 }