Per-angle funnel attribution + paste-ready video descriptions

Landing with ?v=<hook> now sets attribution source "angle:<hook>"
(explicit utm/src still wins), so the existing admin funnel table
shows views -> join clicks -> purchases per angle with no new UI.
Each curiosity-video card on /tools gains a paste-ready description
block ending in the matched invite link - aligning with the "link
in the description" line baked into every recording.

public/track.js

@@ -5,6 +5,7 @@
       if(s)return s;
       const p=new URLSearchParams(location.search);
       s=p.get('utm_source')||p.get('src')||'';
+      if(!s){const v=p.get('v');if(v&&/^[a-z]{2,12}$/.test(v))s='angle:'+v;}
       if(!s&&document.referrer){try{const h=new URL(document.referrer).hostname;if(h&&h!==location.hostname)s=h}catch(e){}}
       s=s||'(direct)';
       sessionStorage.setItem('ctb.src',s);