Fix welcome logo, real hex grid, Matrix boot messages, deeper TDS coverage

- WelcomePage: use official Lotus.png instead of generated SVG
- Hex Grid background: proper pointy-top hexagons via SVG data URI (was
  just triangles from linear-gradient trick)
- Boot sequence: Matrix-specific messages (TLS cert, E2EE Olm/Megolm,
  cross-signing, media proxy, /help hint)
- Terminal mode CSS: nav right border, header bottom glow, kbd TDS key
  style, abbr cyan underline, time amber color, img hover cyan outline,
  explicit body color anchor

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lotus-terminal.css.ts

@@ -297,3 +297,58 @@ globalStyle(`body.${lotusTerminalBodyClass} ul li::marker`, {
 globalStyle(`body.${lotusTerminalBodyClass} ol li::marker`, {
   color: '#FF6B00',
 });
+
+// ── Structural elements — scoped TDS layout chrome ────────────────────────
+
+// Sidebar/nav: subtle cyan right border
+globalStyle(`body.${lotusTerminalBodyClass} nav`, {
+  borderRight: '1px solid rgba(0,212,255,0.10)',
+});
+
+// Page headers / toolbars: subtle bottom border glow
+globalStyle(`body.${lotusTerminalBodyClass} header`, {
+  borderBottom: '1px solid rgba(0,212,255,0.14)',
+  boxShadow: '0 4px 24px rgba(0,0,0,0.55)',
+});
+
+// kbd — TDS terminal key style
+globalStyle(`body.${lotusTerminalBodyClass} kbd`, {
+  fontFamily: "'JetBrains Mono', 'Fira Code', 'Courier New', monospace",
+  fontSize: '0.75em',
+  background: '#0d1520',
+  border: '1px solid rgba(0,212,255,0.35)',
+  borderBottom: '2px solid rgba(0,212,255,0.50)',
+  borderRadius: '3px',
+  padding: '0.1em 0.45em',
+  color: '#00D4FF',
+  textShadow: '0 0 4px rgba(0,212,255,0.4)',
+  boxShadow: '0 1px 3px rgba(0,0,0,0.6)',
+});
+
+// Tooltip / title popups: if browser renders them, style if possible
+globalStyle(`body.${lotusTerminalBodyClass} [title]`, {
+  textDecoration: 'underline dotted rgba(0,212,255,0.35)',
+  cursor: 'help',
+});
+
+// abbr
+globalStyle(`body.${lotusTerminalBodyClass} abbr[title]`, {
+  textDecoration: 'underline dotted #00D4FF',
+});
+
+// time elements — amber muted
+globalStyle(`body.${lotusTerminalBodyClass} time`, {
+  color: '#7fa3bf',
+  fontSize: '0.78em',
+});
+
+// Images: cyan border on hover
+globalStyle(`body.${lotusTerminalBodyClass} img:hover`, {
+  outline: '1px solid rgba(0,212,255,0.35)',
+  boxShadow: '0 0 12px rgba(0,212,255,0.12)',
+});
+
+// Ensure body text color is correct regardless of vanilla-extract theme loading order
+globalStyle(`body.${lotusTerminalBodyClass}`, {
+  color: '#c4d9ee',
+});