fix(download): unblock search after a failed update

A failed update left DownloadState.Error in the state flow forever:
settings replayed it as a snackbar on every recomposition and search
stayed locked until the next app start.

app/src/main/java/com/example/research/feature/download/DownloadManager.kt

@@ -52,6 +52,13 @@ class DownloadManager(
     var onDownloadSuccess: (() -> Unit)? = null
     var onTerminal: ((DownloadState) -> Unit)? = null
 
+    private suspend fun expireErrorStateToIdle() {
+        delay(TERMINAL_STATE_DURATION)
+        if (downloadState.value is DownloadState.Error) {
+            updateDownloadProgressState(DownloadState.Idle, 0f)
+        }
+    }
+
     fun startDownload() {
         if (downloadState.value is DownloadState.Loading) return
         if (!downloadScope.isActive) return
@@ -79,6 +86,7 @@ class DownloadManager(
                         updateDownloadProgressState(
                             DownloadState.Error(sourceUnavailableMessage), 0f
                         )
+                        expireErrorStateToIdle()
                         return@withLock
                     }
 
@@ -135,6 +143,7 @@ class DownloadManager(
                             }
 
                         }
+                        expireErrorStateToIdle()
                     }
                 } finally {
                     downloadJob = null
@@ -174,6 +183,7 @@ class DownloadManager(
                         updateDownloadProgressState(
                             DownloadState.Error(sourceUnavailableMessage), 0f
                         )
+                        expireErrorStateToIdle()
                         return@withLock
                     }
 
@@ -230,6 +240,7 @@ class DownloadManager(
                             }
 
                         }
+                        expireErrorStateToIdle()
                     }
                 } finally {
                     downloadJob = null

app/src/main/java/com/example/research/ui/main/MainScreen.kt

@@ -64,7 +64,11 @@ fun MainRoute(
             dictionary.isActive && dictionary.articleCount > 0
         }
 
-        settingsState.downloadState is DownloadState.Idle &&
+        val downloadSettled = settingsState.downloadState.let { state ->
+            state is DownloadState.Idle || state is DownloadState.Error
+        }
+
+        downloadSettled &&
             !settingsState.indexingProgress.isIndexing &&
             settingsState.importState !is ImportState.Importing &&
             settingsState.importState !is ImportState.Extracting &&