Add the new integrated-join-process training video (Video 4)

New 4-min screen recording of the on-site wallet-connect join flow becomes
Video 4; the old dApp walkthrough is relabeled as the Video 5 backup method
and the payments explainer moves to Video 6. Chatbot canned answers and the
AI system prompt now describe the updated video lineup.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

public/chat.js

@@ -23,7 +23,7 @@
     {k:['fund','funding','buy pol','get pol','deposit','exchange','transfer','send pol'],
      a:()=>`You'll need about ${pol()} POL plus a little extra for gas, on Polygon Mainnet. <a href="/training">Video 3 in the training</a> shows how to fund your wallet. Double-check you're sending POL on the Polygon network — not another chain.`},
     {k:['join','buy','purchase','premium position','enter','sign up','signup','register','get started','start'],
-     a:()=>`Ready to join? Go to the <a href="/start">Getting Started page</a> — it always shows the current team sponsor to use. <a href="/training">Video 4 in the training</a> walks through the purchase in the dApp. Always confirm the sponsor ID in the dApp matches the one on the start page before signing.`},
+     a:()=>`Ready to join? Go to the <a href="/start">Getting Started page</a> — it shows the current team sponsor and lets you connect your wallet and buy your position right on the site, with the sponsor ID filled in automatically. <a href="/training">Video 4 in the training</a> walks through the whole process (and Video 5 covers the dApp backup method).`},
     {k:['sponsor','current sponsor','who do i join under','placement','whose link','referral'],
      a:()=>{const s=sponsorInfo&&sponsorInfo.sponsor;return s?`The current team sponsor is <strong>ID ${esc(s.id)}${s.name?' ('+esc(s.name)+')':''}</strong> — always verify on the <a href="/start">Getting Started page</a> right before you join, because placements rotate as positions qualify. Don't use an old screenshot or saved link.`:`The current sponsor is always shown live on the <a href="/start">Getting Started page</a> — check there right before joining, because placements rotate as positions qualify.`}},
     {k:['qualified','qualification','2 directs','two directs','directs','retire'],
@@ -59,7 +59,7 @@
     {k:['risk','safe','scam','lose money','guarantee','guaranteed','income','earnings','legit'],
      a:()=>`Straight answer: participation involves cryptocurrency and smart-contract risk, and <strong>no income is guaranteed</strong>. Results depend on team effort, duplication, upgrades, smart-contract rules, and POL's market value. Only use funds you can afford to lose.`},
     {k:['video','videos','training','watch','tutorial','learn','how to'],
-     a:()=>`All four training videos are on the <a href="/training">Training page</a>: (1) How the team build works, (2) Create your MetaMask wallet, (3) Funding your wallet, (4) Buying the Premium position. Watch them in order.`},
+     a:()=>`All the training videos are on the <a href="/training">Training page</a>: (1) How the team build works, (2) Create your MetaMask wallet, (3) Funding your wallet, (4) Joining right on the site with wallet connect, (5) the dApp backup method, plus a payments explainer. Watch them in order.`},
     {k:['seed phrase','secret recovery','recovery phrase','private key','12 words','passphrase'],
      a:()=>`<strong>Never share your Secret Recovery Phrase or private keys with anyone</strong> — not this site, not a sponsor, not "support". Anyone asking for it is trying to steal your funds. MetaMask will never ask for it either, except when you restore a wallet yourself.`},
     {k:['promote','promo','promo tools','tools','swipe','swipes','email swipe','banners','banner','graphics','marketing','share this','invite people','video clips','how do i share','social post','facebook post','twitter','my voice','branded voice'],