fix(builder): phase-2 design tweaks (landing home icon, decouple layer-hover from guides, neutral zone separator)

- PagesPanel: add fa-home glyph (8px, inherits badge text color) before
  "Landing" text in the landing-page badge, restoring the icon dropped
  in an earlier polish pass.
- editor.css: split [data-craft-hovered] and [data-layer-hovered] into
  distinct rules. Layer-hover now uses a solid 2px accent outline (vs
  the dashed structural guides) and is excluded from the .guides-off
  suppression list, so the Layers-panel hover->canvas locator still
  works when "Show guides" is off. Structural guides/hover
  ([data-craft-node], [data-craft-hovered]) remain correctly gated.
- Canvas.tsx: move the header/footer ZonePreview separator border to a
  .zone-preview-sep class, recolor it from amber
  (rgba(245,158,11,0.3)) to neutral (rgba(148,163,184,0.25)) to match
  the empty-state variant, and gate it on .guides-off via CSS
  descendant selector so it disappears with the rest of the guides.

craft/src/panels/left/PagesPanel.tsx

@@ -319,8 +319,12 @@ export const PagesPanel: React.FC = () => {
                         padding: '1px 5px',
                         borderRadius: 'var(--radius-sm)',
                         flexShrink: 0,
+                        display: 'inline-flex',
+                        alignItems: 'center',
+                        gap: 4,
                       }}
                     >
+                      <i className="fa fa-home" aria-hidden="true" style={{ fontSize: 8, color: 'inherit' }} />
                       Landing
                     </span>
                   )}