feat(sw): viewer layer eye-icon rule, header hover, trailing strip and file name width

User-requested SW Viewer changes (2026-10-21); no new Props, public .d.ts unchanged.
- Layer popup visibility: AI docs (VIEWER §4.1, catalog, design rules, patterns,
  AI_GUIDE) require the Eye / EyeOff icon button, never a switch; example H now
  renders a real layer list with eye buttons; Storybook eye button gets the pointer.
- Viewer header hover: text and icon #FFC600, the #266651 hover face removed; size and
  position unchanged. Status stays display only.
- Trailing strip: status, the trailing icon button (info / license) and SWHeader
  minimize / close are full-height (48px) segments on the window-area face, no gap, top
  and bottom on the object surface border; no line around the license button.
- File name: the measured steps use the file-name basis (header width), not the text
  width, so a short and a long name give the same Open / file-name widths.
- File open icon: the black icon outline of every viewer icon (SWViewerIcon), no frame.

src/sw/sw-viewer-stories.css

@@ -16,7 +16,7 @@
 .sw-viewer-story-list li[data-visible="false"] { opacity: 0.45; }
 .sw-viewer-story-swatch { flex: 0 0 10px; width: 10px; height: 10px; border: 1px solid var(--hm-sw-viewer-panel-inner-border); border-radius: 9999px; }
 .sw-viewer-story-name { flex: 1; min-width: 0; overflow: hidden; white-space: nowrap; text-overflow: ellipsis; font-family: ui-monospace, monospace; font-size: 12px; }
-.sw-viewer-story-eye { display: inline-flex; align-items: center; justify-content: center; width: 24px; height: 24px; border-radius: 4px; color: var(--hm-sw-viewer-panel-heading); }
+.sw-viewer-story-eye { display: inline-flex; align-items: center; justify-content: center; width: 24px; height: 24px; border-radius: 4px; color: var(--hm-sw-viewer-panel-heading); cursor: pointer; }
 .sw-viewer-story-eye:hover { background: rgba(154, 146, 132, 0.3); }
 .sw-viewer-story-props { margin: 0; }
 .sw-viewer-story-props > div { display: flex; justify-content: space-between; gap: 12px; padding: 6px 0; border-bottom: 1px solid var(--hm-sw-viewer-panel-inner-border); font-size: 12px; }