Viral welcome tour + line banner + wall, milestone stepper, rich solo editor, CTA-gated reads

- Welcome tour (3 levels x 10s) unlocks welcome credits; line banner in Profile; public /wall/<username>
- 'Your next move' redesigned as a milestone stepper
- Solo composer: BV-style rich editor (H2/H3, inline image+video, undo/redo, raw text)
- Solo read reward now requires clicking through to the advertiser, not just dwelling
- Sanitizer: inline media whitelist + script/style stripped whole

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

public/assets/wall.js

@@ -0,0 +1,33 @@
+// Public banner wall: a member's line banner plus their upline ladder, with
+// their join link. The viral surface: members send traffic here, every visit
+// puts eyes on the whole line.
+(async function () {
+  await IAP.renderNav('');
+  const name = location.pathname.split('/').pop();
+  let w = null;
+  try { w = await (await fetch('/api/wall/' + encodeURIComponent(name))).json(); } catch (e) {}
+  const title = IAP.$('wallTitle');
+  if (!w || w.error) {
+    title.textContent = 'No wall under that name.';
+    IAP.$('wallJoin').href = '/my';
+    return;
+  }
+  title.innerHTML = 'The <em>' + String(w.name).replace(/[&<>]/g, '') + '</em> line';
+  IAP.$('wallCtaHead').textContent = 'Join ' + w.name + '’s line';
+  IAP.$('wallJoin').href = w.joinUrl;
+  const grid = IAP.$('wallGrid');
+  grid.innerHTML = '';
+  w.ladder.forEach((m, i) => {
+    const d = document.createElement('div');
+    d.className = 'wall-card';
+    const safe = String(m.name || 'member').replace(/[&<>]/g, '');
+    d.innerHTML = '<div class="wall-pos">Position ' + (i + 1) + (i === 0 ? ' · this wall' : '') + '</div>'
+      + (m.bannerUrl
+        ? '<a href="' + m.targetUrl + '" target="_blank" rel="noopener nofollow"><img src="' + m.bannerUrl + '" alt="' + safe + ' banner"></a>'
+        : m.targetUrl
+          ? '<a href="' + m.targetUrl + '" target="_blank" rel="noopener nofollow"><b>' + safe + '</b><br><span class="muted small">visit their site</span></a>'
+          : '<b>' + safe + '</b><br><span class="muted small">banner slot open</span>')
+      + '<div class="small muted" style="margin-top:8px">' + safe + '</div>';
+    grid.appendChild(d);
+  });
+})();