Desktop: size the folder picker dialog (tiny on HiDPI/XWayland) + log pump failures

JFileChooser came up with an unusable size under the compositor; pin
1040x700. transcribeFile now appends its exception to
~/.config/shonar-desktop/pump-error.log instead of returning false
silently. Verified live: library lists 49 m4a files from
~/Music/Recordings, existing .transcript.md reports detected as done.

desktop/app/src/main/kotlin/com/shonar/desktop/DesktopState.kt

@@ -542,6 +542,12 @@ class DesktopState(private val appDir: File = defaultAppDir()) {
             saveReport(DetailUi(file = f, transcript = transcript, summary = summary))
             true
         } catch (e: Exception) {
+            // Surface pump failures for diagnosis instead of swallowing them.
+            runCatching {
+                File(appDir, "pump-error.log").appendText(
+                    "${java.time.Instant.now()} ${f.name}: $e\n",
+                )
+            }
             false
         }
     }

desktop/app/src/main/kotlin/com/shonar/desktop/Screens.kt

@@ -75,6 +75,9 @@ private fun chooseFolder(): File? {
         dialogTitle = "Choose your recordings folder"
         fileSelectionMode = JFileChooser.DIRECTORIES_ONLY
         isAcceptAllFileFilterUsed = false
+        // Without an explicit size the dialog comes up tiny on HiDPI
+        // compositors (and there is no resize handle), so pin a usable one.
+        preferredSize = java.awt.Dimension(1040, 700)
     }
     return if (chooser.showOpenDialog(null) == JFileChooser.APPROVE_OPTION) chooser.selectedFile else null
 }