fix: prevent agent settings from being silently deleted on channel deletion

desktop/src-tauri/src/lib.rs

@@ -4,7 +4,6 @@ mod events;
 mod huddle;
 mod managed_agents;
 mod media_proxy;
-mod migration;
 mod models;
 pub mod nostr_convert;
 mod prevent_sleep;
@@ -352,11 +351,6 @@ pub fn run() {
             let app_handle = app.handle().clone();
             let shutdown_started = Arc::clone(&restore_shutdown_started);
 
-            // Migrate data from the legacy `com.wesb.sprout` directory before
-            // resolving identity, so the persisted key is available at the new
-            // path on first launch after the identifier change.
-            migration::migrate_legacy_data_dir(&app_handle);
-
             // Resolve persisted identity key (env var → file → generate+save).
             // This is fatal — the app should not start with an ephemeral identity
             // that will be lost on restart, as that silently breaks channel

desktop/src-tauri/src/managed_agents/storage.rs

@@ -55,7 +55,15 @@ pub fn save_managed_agents(app: &AppHandle, records: &[ManagedAgentRecord]) -> R
     let path = managed_agents_store_path(app)?;
     let payload = serde_json::to_vec_pretty(&sorted)
         .map_err(|error| format!("failed to serialize agent store: {error}"))?;
-    fs::write(&path, payload).map_err(|error| format!("failed to write agent store: {error}"))
+
+    // Atomic write: write to a temp file then rename. This prevents partial
+    // writes from corrupting the store if the process crashes mid-write.
+    // rename() is atomic on the same filesystem on both macOS and Linux.
+    let tmp_path = path.with_extension("json.tmp");
+    fs::write(&tmp_path, &payload)
+        .map_err(|error| format!("failed to write temp agent store: {error}"))?;
+    fs::rename(&tmp_path, &path)
+        .map_err(|error| format!("failed to rename temp agent store: {error}"))
 }
 
 /// Maximum log file size before rotation (10 MB).