fix(core): clean up Freedium chrome and drop reader-mode debug counters

Two fixes:

1. freedium_cleanup: remove remaining Freedium article chrome that
   survived the existing nav/footer/toaster pass:
   - <header class="p-6 bg-gray-50 ..."> — author/metadata bar with
     profile pictures and byline, a Freedium wrapper around the article
   - <section> containing [data-slot="dropdown-menu-trigger"] or
     [aria-haspopup="menu"] — the "Download article" dropdown

   Selectors target stable Tailwind utility class prefixes (p-6, bg-gray-50,
   bg-zinc-800) for the header and the WAI-ARIA menu role for the button,
   both resilient to minor Freedium UI updates.

2. Reader-mode meta tag: strip per-capture debug counters.
   _archivrReaderMark now writes 'applied' instead of
   'applied:pre_s=N,...:post_s=N,...' — the counters were useful during
   development but have no place as permanent archive content.

crates/archivr-core/src/downloader/singlefile.rs

@@ -124,7 +124,7 @@ const READER_MODE_SCRIPT: &str = concat!(
         'blockquote{border-left:3px solid #ccc;margin:1em 0;padding-left:1.2em;color:#555}',
       ].join('');
       document.head.appendChild(style);
-      _archivrReaderMark('applied:pre_s='+_pre.seen+',pre_l='+_pre.lazy+',pre_p='+_pre.placeholders+',pre_f='+_pre.fixed+':post_s='+_post.seen+',post_l='+_post.lazy+',post_p='+_post.placeholders+',post_f='+_post.fixed);
+      _archivrReaderMark('applied');
     } catch (e) {
       _archivrReaderMark('failed:exception:' + (e && e.message ? e.message : String(e)));
     }
@@ -531,6 +531,13 @@ fn save_with(
              var _pr=document.getElementById('progress');if(_pr)_pr.remove();\
              document.querySelectorAll('[data-nosnippet]').forEach(function(el){\
                if(!el.firstElementChild&&!el.textContent.trim())el.remove();\
+             });\
+             document.querySelectorAll('[data-slot=\"dropdown-menu-trigger\"]').forEach(function(btn){\
+               if(!/download/i.test(btn.textContent||''))return;\
+               var sec=btn.closest('section');if(!sec)return;\
+               var prev=sec.previousElementSibling;\
+               if(prev&&prev.tagName==='HEADER')prev.remove();\
+               sec.remove();\
              });",
         );
     }