fix(downloads): harden automatic capture and aria2 transfers

- Pass prepared redirect URIs to Aria2 while preserving stable source identities.

- Fence effective-connection telemetry and retry lifecycle transitions by control epoch.

- Keep credentialed routes conservative across redirects, mirrors, and inline URL credentials.

- Preflight destination access and preserve actionable retryable permission errors in the UI.

- Add adversarial regression coverage for ranges, redirects, retries, telemetry, and enqueue failures.

src/utils/downloadErrors.ts

@@ -8,6 +8,13 @@ import type { DownloadErrorKind } from '../bindings/DownloadErrorKind';
 export const classifyDownloadError = (message: unknown): DownloadErrorKind | undefined => {
   if (typeof message !== 'string') return undefined;
   const lower = message.toLowerCase();
+  if (
+    lower.includes('destination access retryable')
+    || lower.includes('could not write to the selected folder')
+    || lower.includes('selected folder could not be verified')
+  ) {
+    return 'destinationAccess';
+  }
   if (
     lower.includes('aria2 error code 19')
     || (

src/utils/propertiesPresentation.test.ts

@@ -58,6 +58,21 @@ describe('Properties connection presentation', () => {
     });
   });
 
+  it('shows effective Aria2 connections when the transfer is degraded', () => {
+    expect(getPropertiesConnectionPresentation({
+      isMedia: false,
+      isTorrent: false,
+      connections: 16,
+      activeConnections: 1,
+      requestedConnections: 16,
+      effectiveConnections: 1,
+    })).toMatchObject({
+      kind: 'aria2',
+      labelKey: 'connections',
+      value: '1 / 1',
+    });
+  });
+
   it('does not use tellActive connections for the Torrent header', () => {
     expect(getPropertiesConnectionPresentation({
       isMedia: false,

src/utils/propertiesPresentation.ts

@@ -25,7 +25,7 @@ export const getPropertiesProgress = (
   : resolveDownloadFraction(snapshot);
 
 export const getPropertiesConnectionPresentation = (
-  snapshot: Pick<PropertiesSnapshot, 'isMedia' | 'isTorrent' | 'connections' | 'activeConnections' | 'requestedConnections' | 'torrentConnectedPeers' | 'torrentConnectedSeeders'>,
+  snapshot: Pick<PropertiesSnapshot, 'isMedia' | 'isTorrent' | 'connections' | 'activeConnections' | 'requestedConnections' | 'effectiveConnections' | 'torrentConnectedPeers' | 'torrentConnectedSeeders'>,
 ): PropertiesConnectionPresentation => {
   if (snapshot.isMedia === true) {
     return {
@@ -53,6 +53,6 @@ export const getPropertiesConnectionPresentation = (
     kind: 'aria2',
     showHeaderMetric: true,
     labelKey: 'connections',
-    value: `${displayCount(snapshot.activeConnections)} / ${displayCount(snapshot.requestedConnections ?? snapshot.connections)}`,
+    value: `${displayCount(snapshot.activeConnections)} / ${displayCount(snapshot.effectiveConnections ?? snapshot.requestedConnections ?? snapshot.connections)}`,
   };
 };