fix(collect): include relative links under /download and add fallback collection path

- Content script: base href check via absolute URL; scope to listing container
- Popup: fallback to background-assisted collection when no receiver exists
- Background: expose collect.fromTab to run injection + collection
- Add debug logging for visibility

src/popup/index.js

@@ -47,7 +47,15 @@ async function refresh() {
   try {
     const tabId = await getActiveTabId();
     if (!tabId) throw new Error('No active tab');
-    const items = await browser.tabs.sendMessage(tabId, { type: 'collectLinks' });
+    let items = [];
+    try {
+      items = await browser.tabs.sendMessage(tabId, { type: 'collectLinks' });
+    } catch (e) {
+      // Fallback: ask background to inject and collect
+      const res = await browser.runtime.sendMessage({ type: 'collect.fromTab', tabId });
+      if (res?.ok) items = res.items || [];
+      else throw new Error(res?.error || e?.message || 'collect failed');
+    }
     allItems = items || [];
     updateCount();
   } catch (e) {