feat(sw): viewer mode header, dropdown and popup panel

- SWViewerHeader: data-driven viewer menu (button / toggle / menu / tabs / switch / custom), More by
  collapseBelow, trailing slot, onCommand; SWHeader logo props with no default logo
- SWViewerMenu: dropdown, check / radio, multi-level submenu, context menu at a point
- SWViewerPanel: viewer popup frame with free children / footer, drag, corner resize, collapse, modal
- Panel controls: SWViewerSection / Field / Hint / Switch / Slider / Input / Button / Badge / Status
- SWHeader black text outline tokens on viewer text, matching icon outline (drop-shadow)
- Storybook SW/Viewer stories; remove SW/Tool story (SW/Popup kept)
- AI guide ai/VIEWER.md, example H, verification scripts and evidence

src/sw/sw-viewer-stories.css

@@ -0,0 +1,33 @@
+/* Story-owned layout for SW/Viewer. Like a consuming program it arranges public components and its own list
+   content; it never styles hm-sw-* classes. Panel content colors read the public --hm-sw-viewer-* tokens. */
+.sw-viewer-story-frame { position: relative; display: flex; flex-direction: column; overflow: hidden; background: #0a0a0b; }
+.sw-viewer-story-canvas {
+  position: relative;
+  flex: 1;
+  min-height: 0;
+  background:
+    linear-gradient(rgba(38, 102, 81, 0.18) 1px, transparent 1px) 0 0 / 40px 40px,
+    linear-gradient(90deg, rgba(38, 102, 81, 0.18) 1px, transparent 1px) 0 0 / 40px 40px,
+    #0a0a0b;
+}
+.sw-viewer-story-room { padding-bottom: 320px; }
+.sw-viewer-story-toolbar { display: flex; flex-wrap: wrap; align-items: center; justify-content: flex-end; gap: 12px 4px; }
+.sw-viewer-story-toolbar > input { flex: 1 0 100%; }
+.sw-viewer-story-list { display: flex; flex-direction: column; gap: 4px; margin: 0; padding: 0; list-style: none; }
+.sw-viewer-story-list li { display: flex; align-items: center; gap: 8px; padding: 4px 6px; border-radius: 3px; }
+.sw-viewer-story-list li:hover { background: rgba(154, 146, 132, 0.25); }
+.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: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; }
+.sw-viewer-story-props dt { color: var(--hm-sw-viewer-panel-label); }
+.sw-viewer-story-props dd { margin: 0; overflow: hidden; white-space: nowrap; text-overflow: ellipsis; font-family: ui-monospace, monospace; user-select: all; }
+.sw-viewer-story-empty { display: flex; flex-direction: column; align-items: center; gap: 8px; padding: 40px 0; text-align: center; font-size: 12px; color: var(--hm-sw-viewer-panel-label); }
+.sw-viewer-story-steps { margin: 0; padding-left: 20px; font-size: 14px; }
+.sw-viewer-story-select { height: 28px; padding: 0 8px; border: 1px solid var(--hm-sw-viewer-panel-inner-border); border-radius: 4px; background: var(--hm-sw-viewer-panel-field-background); font: inherit; font-size: 12px; }
+.sw-viewer-story-reopen { position: absolute; left: 712px; top: 16px; padding: 6px 10px; border-radius: 4px; background: #f5f0e5; font-size: 12px; }
+.sw-viewer-story-context { display: flex; align-items: center; justify-content: center; height: 160px; border: 1px dashed #9a9284; border-radius: 4px; background: #f5f0e5; color: #3e3523; font-size: 13px; }
+.sw-viewer-story-mode { display: flex; gap: 16px; margin-bottom: 8px; font-size: 13px; }